I guess I could give I quick list of games on the top of my head, I consider worth trying out for Amiga(No particular order):
The Settlers (The original... with ability to play co-op... on one Amiga

)
Moonstone (Blood 'n Gore)
Turrican 2 (It IS nothing like the SNES games)
Stardust (Astoroids... but just... more)
Project X (Hard... but great Shooter)
Super Frog (Fun platformer)
Worms (you know what it is)
Exile (only ever tried the demo... but it was fun)
Wings of Fury (just plain fun)
Nuclear War (Twisted apocolyptic humour)
Cannon Fodder (yeah, you know it)
Sensible World Of Soccer (best version)
Pinball Dreams (you know form your GP :lol

Pinball Fantasies (You'll hopefully get to know it for your GP)
As some may notice the games I've listed are those running on an ordinary A500 (well, maybe with 512 kb expansion). I didn't know any A1200 owners and thus not any enhanced games for that chipset... But now I will (when my CD32 arrives B) )
Again... If it's something you're considering spending money on, I surgest you try out some emulation first - just to check out what it is (Hell... I even did that before buying my GP32)
Found a few screenshots (just by google'ing):
At VG museum
The other places I found also provided disk images - which I would'nt be able to post.
And Again

: Lots of legal Amiga stuff at
BTTR. . . They're just not that good at providing screenshots <_<