You should probably check out the Lemon Amiga top 100 games, that has the main games you should own listed.
Some games I've enjoyed which you might not have played include:
Shooters-Apano Sin, Fly Harder, Uridium 2, Virocop
Platformers-Woody's World, Lollypop, Naughty Ones, Snow Bros
Strategy-Historyline, Lords of the Rising Sun, Sabre Team
Puzzle-Jumping Jack'son, Logical, Skweek
Adventure-Kult, The Clue, DreamWeb
There are also some good PD games like Salmon-Pink Max, Egyptian Run and Super Obliteration.