Thanks almost single handedly to JohnCarmack and his support of OpenGL, a number of commercial games come out natively for Unix.

• Anything ID makes (including Quake 1/2/3, Doom 1/2)
• Unreal Tournament and Unreal Tournament 2003

• NeverWinter? Nights

There was a company called Loki that ported many games to Linux. Unfortunately they've gone out of business, so you can't buy their games from them any more. They were responsible for the UT port, as well as Civilization: Call to Power, Myth II: Soulblighter, Railroad Tycoon II, Eric's Ultimate Solitaire, Heretic II, Heroes III, Heavy Gear II, !SimCity? 3000, Soldier of Fortune, Sid Meier's Alpha Centauri, Descent3, !MindRover?, Kohan: Immortal Sovereigns, Tribes 2, Rune, Heavy Metal: F.A.K.K.2 and Postal Plus.

There's also a company called TransGaming who are working on a version of Wine called WineX, especially for gaming, which runs a whole heap of cool new games:

• Warcraft III
• Grand Theft Auto 3
• Civilization III (Season for 3's, isn't it?)
• Black and White
• The Sims
• Everquest
• Jedi Knight II and other Quake 3 engine games
• Half-life/Counter-strike (I got this to run, but it stops being 3D accelerated beyond 800x600 for some reason --GianPerrone)

You can download the source code for WineX under the AFPL, but to download binaries from them you have to subscribe. Subscribing gives you the benefit of supporting them and a say in what games they work on supporting next, so it's highly recommended.

Servers for any commercial game worth their salt come out for Linux.

There are a number of cool GPL/free games for Linux:

• TuxRacer (which has a non-GPL windows versions as well)
• BzFlag - a multi-player tank game
• FreeCiv (originally a clone of Civilization)
• XBill! (This is a good game if you want to get RSI)
• VegaStrike - a space craft fighter/trading game a. la. Elite, Frontier, etc. Still in heavy development but playable.
• FrozenBubble
• TetriNet

If programming games is more your thing, go have a look at the SDL (SimpleDirectMediaLayer).

Alternatively, go out and buy a console. Computers are for business. :)