I think Battle Squadron for SEU, it looked better than most arcade SEUs of the time.
Shadow of the Beast 1 for platformers will always spring to mind, it was seeing that on a friends Amiga in 1989 that made me buy my first Amiga. Not to mention the sound, which compared to my Atari ST of the time, seemed light years ahead of anything I'd heard before it. Beast 2 & 3 IMHO were ugly looking.
Psygnosis games always looked good, but usually played terribly. I liked Gods better than SOTB, and it looked pretty good too.
I never played a decent looking beat 'em up (IK+ was probably my favourite to play). I got Capital Punishment, but this would neither work with my expanded A1200, or WinUAE (yes, I did try using a harfile, and after entering the security code, and it being accepted, the screen would fade, the hard drive would access briefly, and that would be as far as I ever got, both in UAE and on my O40 accelerated A1200)
Driving games, probably the Lotus series, because at least back in 1989, I thought they looked cool.
It was impressive to see Quake running on my Amiga, although in reality, 2 years after having played it on my PC, it was nowhere close the performance of my PC when I first got it, and by the time I had it on the Amiga, my Quake PC was GLquake, and I'd had Quake 2 for 9 months or so. The Genetic Species demo looked good, even in AGA mode (actually, I thought it looked better on my 1084S in AGA than on my Illyama 502 via The Cybervision at 640x480 as it looked to me to be identical to 320x250, only with the clarity and size of the monitor, and lack of scanlines, didn't help the game any)
