Ok, I have installed Ubuntu linux on my machine, not sure about the linux platform gaming. So please suggest some good game? Thanks

Hey, World of Warcraft is good, I also have Ubuntu installed and it runs perfectly. But you need to run it with Wine, look round the net to find out the how to.
Most games will run on linux if you fine a hot too. It realy depends what genre your into, but
MMORPG = WoW
FPS= Counter strike sorce will work but urban terror offes support
Have a look round, google it a bit, also id like to know some more so post if you winde some goodones

Redpanda's suggestions are good.

If you're looking for a good strategy game, I've been playing a lot of Zaticon lately (same username, I'd be happy to show you the ropes. You can probably find it with a quick google search). There's a free demo, which allows you to play any game mode against or with players who may or may not have the full version. You need to buy addon packs for the cooler units, but the demo comes with a few neat units (like geomancer, summoner, or a warlock) and the games 'meat' units, which you can certainly win games with.

I have a small game on my ubuntu it may be the warlock game which norsker mentions, it's like a board game really, you take turns to move, its a very good strategy type game and it will keep you interested for age, and it's free of course,

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Ozirock

Supreme Games, Private Freerolls

there are some FPS games for the linux but you need to try them on your own. as very few are supported with driver and graphics so check which one works for you.