We don't carry a comprehensive list of third party games that support gamepads. Before you decry us, remember that gamepad support depends on the game developers themselves to include this, and the quality of the gamepad support also rests on their shoulders (We can't tell someone else how to program their game.
You might want to check out games from companies like Freeverse and Ambrosia Software. They usually offer very complete demos of their games (so you can really test the game before buying it), and they've consistently made good games for the mac (I've been playing Ambrosia games since the mid 90's on the Mac)
