How can I find a list of games that are playable on my Mac? I'm a casual gamer with a MacBook Air (fall 2010 13" model), I'd like to find some games that are playable on my Mac. Is there any software or website that makes it easy to find games with compatible system requirements?

What I have in mind is something like the (now defunct) Aspyr Game Agent application, which at a glance showed whether a game's system requirements were compatible with a specific Mac; see the screenshots for one game, for a list of games, or read Softonic's review.
Steam has a dedicated Mac section and also lets you filter by OS when searching. And it lists system requirements.