question: Why is retrocompatibility so hard to achieve on modern consoles when a significantly different and rather cheap system like the Wii was able to do it ?
comment: Because compatiblity through emulation is difficult and almost always inexact. For true compatiblity you want the same hardware. The Wii was backwards compatible with the GameCube because the Wii was just a faster GameCube with more RAM so it was easy to just reduce the clockspeed to run older games. Other consoles reuse the chips from older consoles for other purposes so that they can fall back on them for compatiblility. Both the PS2 and the Nintendo DS used the outdated CPU of their predecessor (PS1 and Gameboy Advance) as their sound chip. Finally some consoles just stuffed the previous console inside them - the Gameboy Advance (as well as the SP model but not the Micro model) included the Z80 like processor from the Gameboy and only used it to play Gameboy games. The launch version of the PS3 also included a full 'Emotion Engine' PS2 CPU though it was dropped from later models.
passages: Section::::Technology.:Backward compatibility.
   The Wii MotionPlus was conceived soon after the completion of the initial Wii Remote design, to address developer demand for more capable motion sensing, but was only announced after the sensors could be purchased in sufficient volume at a reasonable price. During a developer roundtable discussion at E3 2008, "Wii Sports Resort" producer Katsuya Eguchi discussed the potential influence of the Wii MotionPlus on the Wii's existing market, stating that Nintendo was looking at whether the MotionPlus capability will be built into the Wii Remote in the future, or kept "as an attachment we only use for certain software."
   Section::::Wii U.:Control.
  
  a Wii Remote is compatible with SNES and GBA releases, but may require button remapping to accommodate for the lack of buttons.br
  
  b NES Classic Controller, the SNES Classic Edition Controller and Club Nintendo's SNES Classic Controller have at least partial functionality with all Wii U Virtual Console releases except DS games, but may require button remapping to accommodate for the lack of buttons.
  
  Section::::Wii U.:Storage.
  
  Virtual Console games are saved either on the Wii U's flash storage (8GB or 32GB) or can be saved on a USB flash drive or external hard drive.
   The Wii MotionPlus was developed by Nintendo in collaboration with game development tool company AiLive. The sensor used is an InvenSense IDG-600 or IDG-650 in later units, designed in accordance to Nintendo's specification; with a high dynamic range, high mechanical shock tolerance, high temperature and humidity resistance, and small physical size.
   BULLET::::- Memorex launched a series of controllers in 2011 under the "Game Controller Plus" moniker. Available in black, pink and blue, the Game Controller Plus line has Wii MotionPlus functionality built in.
  
  Section::::Reception.
  
  Developers at Electronic Arts have noted that the fidelity of the device can be too sensitive and at times inaccurate, although technology reviewers have likened the improved accuracy to the leap from the fidelity of VHS to that of Blu-ray.
  
  Game reviewers at Official Nintendo Magazine have called the device "100% accurate" and stated that movements are "captured extremely accurately".
   Development of a motion-enabled controller began when development of the Wii console started in 2001. In that year, Nintendo licensed a number of motion-sensing patents from Gyration Inc., a company that produces wireless motion-sensing computer mice. Gyration had previously pitched their idea and patents of a motion controller to Sony and Microsoft, who both declined. Nintendo then commissioned Gyration to create a one-handed controller for it, which eventually became the "Gyropod", a more traditional gamepad which allowed its right half to break away for motion-control. At this point, Gyration brought in a separate design firm, Bridge Design, to help pitch its concept to Nintendo. Under requirement to "roughly preserve the existing Game Cube button layout", it experimented with different forms "through sketches, models and interviewing various hardcore gamers". By "late 2004, early 2005", however, Nintendo had come up with the Wii Remote's less traditional "wand shape", and the design of the Nunchuk attachment. Nintendo had also decided upon using a motion sensor, infrared pointer, and the layout of the buttons, and by the end of 2005 the controller was ready for mass production.
   Accessories can be connected to a Wii Remote through a proprietary port at the base of the controller, such as the bundled Nunchuk — a handheld unit with an accelerometer, analog stick, and two trigger buttons.An expansion accessory known as Wii MotionPlus augments the Wii Remote's existing sensors with gyroscopes to allow for finer motion detection; the MotionPlus functionality was later incorporated into a revision of the controller known as Wii Remote Plus. At E3 2009, Nintendo also presented a "Vitality Sensor" accessory that could be used to measure a player's pulse. In a 2013 Q&A, Satoru Iwata revealed that the Vitality Sensor had been shelved, as internal testing found that the device did not work with all users, and its use cases were too narrow.
   The Classic Controller is another extension for the Wii Remote and is more similar to classic gamepads. Players can use it with older games from the Virtual Console in addition to games designed for the Wii.
  
  Section::::Hardware.:Memory storage.
   The device is only used by games that have been specifically developed to use its functionality. It can remain attached to the Wii Remote when playing games that do not support it without causing any problems, but it will not enhance gameplay. The add-on version of the device is incompatible with any Wii Remote accessories that snugly encase the Remote itself, such as the Wii Wheel, the Wii Zapper, guitar controllers for "Guitar Hero" and "Rock Band" games and "NHL Slapshot"'s hockey stick accessory.
  
  Section::::Wii Remote Plus.
   At the same time, criticism of the Wii Remote and Wii hardware specifications had surfaced. Former GameSpot editor and Giantbomb.com founder Jeff Gerstmann stated that the controller's speaker produces low-quality sound, while Factor 5 President Julian Eggebrecht criticized the hardware audio as substandard for a console of its generation. UK-based developer Free Radical Design stated that the Wii hardware lacks the power necessary to run the software it scheduled for release on other seventh-generation consoles. Online connectivity of the Wii was also criticized; Matt Casamassina of IGN compared it to the "entirely unintuitive" service provided for the Nintendo DS.
   NST started developing Project H.A.M.M.E.R. For the Nintendo Wii but several problems landed the project in 'development hell'. A large amount of funding was spent on cut-scenes early in development and so when the project started to fall behind managers didn't want to end it because of the capital already spent. The American developers suggested that the problem was the gameplay however the Japanese managers believed the problems were the environments. This dispute, among others, made the project drag on for a number of years before it was totally abandoned and a large number of staff were made redundant.
   On July 11, 2007, Nintendo unveiled the Wii Balance Board at E3 2007 with "Wii Fit". It is a wireless balance board accessory for the Wii, with multiple pressure sensors used to measure the user's center of balance. Namco Bandai produced a mat controller (a simpler, less-sophisticated competitor to the balance board).
  
  Section::::Hardware.:Wii Remote.
   "We Ski" by Bandai Namco Games is the first third-party game to have made use of the Wii Balance Board, in conjunction with the Wii Remote and Nunchuk attachment.
   During development of the Wii console, video game designer Shigeru Miyamoto brought in mobile phones and controllers for automotive navigation systems for inspiration for the Wii Remote, eventually producing a prototype that resembled a cell phone. Another design featured both an analog stick and a touchscreen, but Nintendo rejected the idea of a touchscreen on the controller, "since the portable console and living-room console would have been exactly the same".
   During development of the Wii Remote, video game designer Shigeru Miyamoto brought in mobile phones and controllers for automotive navigation systems for inspiration, eventually producing a prototype that resembled a cell phone. Another design featured both an analog stick and a touchscreen, but Nintendo rejected the idea of a touchscreen on the controller, "since the portable console and living-room console would have been exactly the same". Coincidentally, this idea would later be implemented on the Wii U's GamePad controller, as well as the Nintendo Switch.
   Section::::Technology.:Network features.
  
  The Wii system supports wireless connectivity with the Nintendo DS handheld console with no additional accessories. This connectivity allows players to use the Nintendo DS microphone and touch screen as inputs for Wii games. "Pokémon Battle Revolution" is the first example Nintendo has given of a game using Nintendo DS-Wii connectivity. Nintendo later released the Nintendo Channel for the Wii allowing its users to download game demos or additional data to their Nintendo DS.
   The disc reader of the Wii does not play DVD-Video, DVD-Audio or Compact Discs. A 2006 announcement stated that a new version of the Wii (capable of DVD-Video playback) would be released in 2007; however, Nintendo delayed its release to focus on meeting demand for the original console. Nintendo's initial announcement stated that it "requires more than a firmware upgrade" to implement, and the capability could not be made available as an upgrade option for the existing Wii; the delay later became a cancellation when production of the Wii was discontinued in 2013. However, despite the assertion, third parties have used Wii homebrew to add DVD playback to unmodified Wii units. The Wii also can be hacked to enable an owner to use the console for activities unintended by the manufacturer. Several brands of modchips are available for the Wii.
   Section::::History.:Counterfeit units.
  
  As the Wii gained in popularity, reports surfaced of counterfeit Wii Remotes entering circulation. Although these devices may provide the same functionality as official Wii Remotes, the build quality is typically inferior and components such as the rumble pack and speaker are noticeably different. It is also unclear if current and future accessories will operate correctly with counterfeit units due to the differences in internal components.
  
  Section::::Design.
   "Mario Kart Wii" uses the Wii Remotes motion sensing to provide intuitive and conventional steering controls; each copy of the game is bundled with the Wii Wheel accessory to augment this feature.
  
  Section::::Gameplay.
   Games downloaded from the Virtual Console library can be stored in the Wii's built-in 512 MB flash memory.
  
  Wii system software versions 2.0 and later allow Virtual Console and WiiWare games to be moved from the console's internal memory to a removable SD card and then back to the same console.
   Section::::Development.:Audio.
  
  The music was composed by Asuka Ohta and Ryo Nagamatsu; who both used new interpretations of the familiar melodies from earlier games alongside original material. A 46-track official soundtrack was released in December 2011 as a Club Nintendo reward in Japan. The speaker on the Wii Remote is frequently used during gameplay, as sound effects like crashes and warning signals are emitting from it. During the extensive testing of the different Wii Wheel prototypes, the developers decided to have the voice actors playing the game during recording sessions.
  
  Section::::Reception.
   The Wii's internal hardware is an updated derivative of that of the GameCube; in comparison to its seventh-generation competitors, the Wii had lower overall graphics capabilities, and does not output in high-definition. The Wii also featured internet-enabled features; the Nintendo Wi-Fi Connection service allowed supported games to offer online multiplayer and other features, while the WiiConnect24 feature allowed messages and updates to be downloaded while the console was in standby. Through Wii Shop Channel, additional games and apps can be downloaded or purchased for the console, including Virtual Console—a selection of classic video games emulated from older consoles. Early models of the Wii also had backwards compatibility with GameCube games and controllers, but this was dropped from later hardware revisions.
   This is a list of released video games for the Wii video game consoles which allow use of Classic Controller/Classic Controller Pro and/or GameCube controller. This list does not include games released on Nintendo's Virtual Console as the Classic Controller and GameCube controller can also be used for all Virtual Console games, with the exception of some TurboGrafx-16 games. Many of the games on this list are ports of prior generation games or games that were concurrently released on other consoles with traditional control schemes such as PlayStation 2, 3, and 4 and the Xbox 360 and One.
   Durability and quality of plastics and other components of the V.Smile systems is in-line with expectations given the low cost of the devices. Replacement game system hardware can often be bought for less than the cost of a single game on dedicated current generation console game systems from Sony, Microsoft or Nintendo on the market.
  
  Section::::Games.
   Section::::Home consoles.:Wii.
  
  The Wii was released on November 19, 2006 as Nintendo's seventh-generation home console. Nintendo designed the console to appeal towards a wider audience than those of its main competitors, the PlayStation 3 and Xbox 360, including "casual" players and audiences that were new to video games.
  