Why not try...
: Nifty platform romp. Pretty pretty, too.
: FPS in a Doom
This next lot are more recent, and are all still for sale. All require some processor oomph and extra memory on real Amigas. I mention them because many folks probably won't have heard of them, and therefore would not otherwise buy them. And because they are cool AGA games.
Land of Genesis
Tales from Heaven
(Cute little Mario64-esque affair)
I personally recommend Guardian
(as listed by Cody) above all others. It rules. Defender
And it is not
too difficult, to counter the claim most folks seem to make about it. They're just rubbish at it.