I cannot find any good games that run well on Macs. I have looked at various "Best Games" sites, but none is really helpful.
Anyway, some of you may be able to suggest a few good games. In the past the only games that really gripped me were The Settlers and Myst. That sounds very limited, but I enjoyed those games so much that I didn't have time to look at many others. When the iPad arrived I did grab The Room and its sequel.
One type of game I find thoroughly uninteresting, however, is the Shoot 'Em Up. I prefer something that makes me think.