I think from a technical point of view the game that pushed and really showed off what AGA chip could do was most likely Microcosm on the CD32
Other games that showed off what it could do are the FPS
Gloom, Breathless, Fear, Alien Breed 3d to name a few.
Capital Punishment and in fact any Clickboom game really did show how far the AGA chip could go ( Napalm, T-Zero, Myst, even Quake all could be ran off just the AGA chip. ok they needed more power than your average A1200, but they all managed to run without a graphic card which is pretty impressive)
Other I can think off,
Theme Park, Aladdin, Loin King, Star Trek 25th Aniv, Sim City 2000, Guardian, Slam Tilt, Banshee, Super Stardust, Worms DC, and Alien Breed Tower Assault.
