so why dont more games like this come out for mac?
Well it's a long story. To make it short, I'll say the Mac game market has always been small. Many developers don't think there is payback in the extra cost of developing a Mac game. Then there are the porters like Aspyr or MacSoft who have to negotiate deals with PC developers. And then there was the hated Havok issue, huge deal breaking licensing fees to create a Mac game based on a PC game with Havok physics. To some degree that has changed in the last couple of years getting better.
As the Mac market to continues to grow, if Mac owners actually purchase games, you'll probably see more native Mac games.
Honestly 100% of the serious gaming I do is on my 360, or my PC, or my MacBookPro running Vista. If you're a casual gamer, go check
Apple's Game Page. Lots and lots of native Mac games there.