GALAGA '90 / Namco / Turbografx 16
Well, this is definitely superior to the NES version of Galaga.
Yep, basic Galaga gameplay is basically unfuxed with, but they've made some cosmetic additions and stuff that are nice.
The sprites are more detailed and colorful, there's varying backgrounds to the levels now, music in the bonus stages and on the game over screen, and you can choose to start out with two ships side by side (like in the famous old arcade bug) at the expense of one of your extra lives.
If you are jonesing for some Galaga this is probably the best version of the game short of the arcade original. I haven't seen any better yet anyway.