Are these LEGO Star Wars bricks genuine or fake? I bought some LEGO pieces from eBay, and I'm not sure if they are genuine LEGO.

I compared them with my LEGO, and every piece of my LEGO has the logo ©LEGO on it. However, only some of the ones I bought have this logo, and some do not.  



You can see the © symbol on the top gun, the bottom is a gun from my own LEGO collection. If you flip them over, my gun (bottom) has some numbers (I think manufacturing number) and the word LEGO on it.  The new one (top) has nothing. Is the top gun just an older LEGO, or a fake knockoff?

Additionally, some of the battledroid torsos have the © LEGO mark on them, as well as some numbers, and some of them have just © and nothing else.



It is the same with the battledroid heads. On the left, my genuine part has the ©LEGO and numbers on the other side.  On the new ones in question (right), there is nothing.
I can't find an official source for this statement, but with the exclusion of a few rarities like test bricks, and perhaps a few other cases, every piece of genuine LEGO will have the brand stamped on it somewhere.

You've taken photos of pieces together that clearly ought to have come from the same mold, where one displays the LEGO brand and the other does not. That seems like solid proof that you've purchased fake parts to me.

As an example of how similar clone bricks can be, here are some battle droids made by LEPIN: https://cheap-bricks.com/lepin-05025-star-wars-homing-spider-droid/



It's hard to see, but I can make out the © on the trigger of the stormtrooper's weapon.