Ender 2 LCD replacement My Ender 2 LCD is suddenly not lighting up.
Is it possible to replace it with an Ender 3 LCD?
Not easily.  Some folks have been messing with both 2 and 3 LCDs and based on their posts, the pinout is different between the two.
Ender 2 display pinout from when one GuzLightyear figured it out for Marlin (MKS MINI 12864 LCD):

          -----
     5V  | · · |  GND
   MOSI  | · · |  LCD_RS
 LCD_A0  | · · || BTN_EN2
  RESET  | · · |  BTN_EN1
BTN_ENC  | · · |  SCK
          -----

From a user called arnd13, the Ender 3 equivalent would be:

         -----
5V      | · · |  GND
MOSI    | · · |  LCD_A0
SCK     | · · || BTN_EN2
CS      | · · |  BTN_EN1
BTN_ENC | · · |  Buzzer
         -----

Maybe you have some luck in debugging your screen (sometimes with these LCD screens, a contrast adjustment resolves the issue).