-Baldur's Gate 1&2 (their respective extensions)

-Outcast

-Wing Commander III/IV/V (not PC exclusives but good games)

-Myst series (5 episodes)

-Day Of The tentacle, Full Throttle, Grim Fandango, Monkey Island and others point&click tiltes from Lucasarts

-Gabriel knight, Rama, Space Quest and others point&click titles from Sierra

-Little Big Adventure 1&2 (not PC exclusives, available on PSone)

-Total Annihilation

-Jedi knight

-the Witcher

-Planescape Torment

-Fallout 1&2

-Sanitarium

-Dungeon keeper

and so more....

Wow so many games id not thought of or forgotton about thanks for all the help guys, now im not sure where to start LOL, think ill go demo hunting first :)

TOTAL WAR TOTAL WAR TOTAL WAR

Probably in this order

Rome
Empire = Shogun 2
Napoleon
Medieval 2
Shogun and Medieval are too old

TOTAL WAR TOTAL WAR TOTAL WAR

You should probably buy a Total War game

And Company of Heroes is just plain brilliant. Also, if you are a PlayStation gamer like me, you might want to consider getting Star War Knights of the Old Republic and Jade Empire, Bioware games which were Xbox/PC games only

definitely Crysis and Anno 1404 (Dawn of Discovery)
Civilization is also always worth a look.

If you haven't played Dragon Age games yet, go for the PC version as it gameplay is actually quite better than in consoles and as a result the game is much more challenging and fun.

The Witcher: Enhanced edition is a great game to get ready for May 17th, the date when its exclusive sequel releases too.

Napoleon Total War....Nuff said! or World of Tanks (Its FREE!!!!)

Sweet, I've been waiting for Magicka to go on sale.  Is the Magicka Vietnam DLC worthwhile?

As for the OP, I would highly recommend Dawn of Discovery/Anno 1404.  It's real time, but if you like Civ, you'll probably like this.  Quite addictive.

Shogun 2 is the best total war game. You don't need the others (though they're very good as well).

Zeno Clash, Mount and Blade: Warband, Racettear, Eufloria, Borderlands, Gish, Left4Dead 2, Mass Effect, Mass Effect 2, Rift, Fate of the World, Sam & max series, Shattered Horizon, VVVVVV, League of Legends, and Alien Swarm.

Deus Ex and X-COM. The UFO Defense and Terror form the Deep, the rest are shitty. Jedi Knight 2: Jedi Outcast is probably the best of the series and beiong a jedi is fucking awesome.

ALso play Civ4, Civ5 will has a lto of nice additions (like 1 unit per tile) but it is sitll worse than the depth of civ4.