Never played Neverwinter. I did used to play Prey, tho. Played the heck out of it. A good FPS. And of course I played a load of Civilisation. Great game. Haven't played much on my Mac since Leopard. Usually stick with the console games.
Borderlands, Dungeon Defenders (Steam), Doom 3, Baldur's Gate Enhanced Edition (launches Friday), the Deathspank series, Knights of the Old Republic, all of Blizzard's catalog (StarCraft, Diablo, WarCraft...)...
And if you want the best, most addictive game you ever bought for 99 cents, go to the app store and download Robokill.