I'm an avid fan of the EV series.
I still find Escape Velocity was the best. The "sequel" (it wasn't really a sequel, more like a revamp of EV), EV: Override was good, but it didn't grab me like EV.
EV Nova is a complete remake of EV, with a brand new engine, and a Windows version. In EV Nova you can also play EV and EV: Override as Amrbosia Software has released the data files that you move into the Nova folder to play the two in the same application.
All 3 get a thumbs up from me.
Other good games I've play have been Unreal Tournament, StarCraft and WarCraft 3. (I own UT, and SC with Brood War, but tried out WC3 on a friend's PC.)
Keep tabs on
http://www.insidemacgames.com for a lot of Mac gaming info.
EV Nova, for the first bit is better then the original Escape Velocity, but I lost interest when I beat all the story lines, and there were no major plug-ins available. The Vell-Os storyline has to be the best storyline ever, especially the high end ships.
The Polaris comes in a close second for me, but when your brother sticks in a cheat plug-in and you don't know, it ruins the fun.