One of the best AGA games is
Pierre Le Chef. It's really console-esque. 50hz scrolling, parallax, great music with simultaneous SFX and good gameplay to boot.
http://www.lemonamiga.com/games/details.php?id=2516
The other honorable mention goes to Bubble & Squeak AGA. While the background effects aren't as clever as some of the animated backgrounds in the Mega Drive version, the graphics are sharper and it shows the A1200 was much closer to the modern consoles than the A500 was.