• Alright, my pc is crahp.  Lets just leave it at that.  The most recent/demanding game I've been able to run is Half Life 2 on medium settings.  :D 
• I'm going to build a (primarily gaming) pc when I'm able to taste Diablo III on the horizon.  So I've got some time.   
• I'm also going to need some time.  I know there are some great pc games out there.  It was my platform of choice for the late 90s-early 00s. I've got some games to catch up on.
• I'm out of it.  This is where I'm requesting the help and vast knowledge of the GB community.
• Here's a few games I've played just to give you a taste of mah preferences.

1. Morrowind
2. Black and White
3. Dawn of War
4. Myst 1-4
5. Knights of the Old Republic
6. Neverwinter Nights - platinum edition baby!
7. Starcraft battlechest
8. Diablo battlechest
9. F.E.A.R.
10. Unreal Tournament 2004
11. Halo
12. Half Life 2
13. Total War - Rome
14. Dark Reign
15. Homeworld
16. Ground Control

Crysis

Hrm, there are quite a few games that may fit your bill.
Titan quest
Company of Heroes
The Witcher
X2 or X3
Mount and Blade: Warband
Penumbra (if you like to get your scare on)
Freelancer
X-com
Vampire: The Masquerade Bloodlines
Torchlight
Icewind Dale,
 
There are quite a few games that you've missed.  They're all pretty great.

I recommend Torchlight. Even the crappiest of PCs can run it.

Pretty much all of these.  
 
grab rollercoaster tycoon 3.

You played the other Half Life 2 episodes? 
 
I also recommend Company of Heroes Online. Its a free version of the original Company of Heroes

 
 With the 3D0 version Toys For Bob also included the original source code. A free open source version has been produced for both Windows and MacOSX from refinement of this code, and the game has been ported from there to other platforms as well. This version is called "The Ur-Quan Masters" without reference to the Star Control name because Toys for Bob does no longer holds the appropriate rights. 

" Pretty much all of these. "  

Go play the witcher and dont come back till you do.

Are you just looking for games in the last 7 or 8 years or even further back as well? I'm going to assume you don't mind going back to 3d games that are old, but don't look like complete shit (but bear in mind, they are old, so will look a little shit), and start off by recommending Thief: The Dark Project and Thief II: The Metal Age. I never played The Dark Project, but I played through Thief II at least three times and would call it one of my favourite PC titles ever. Thief: Deadly Shadows is more recent, but didn't grab me as much as Thief II. It is, however, a far better looking game, so you might want to give it a try if you can't handle the oldness of the originals. 
 
I'm really tired, so I can't think of anything else from the early 2000s, so I'll just leave you with recommendations for the STALKER series, The Witcher, Dragon Age and Cryostasis.

MInecraft. Its all you'll ever need.@jadeskye said:

" Pretty much all of these.   grab rollercoaster tycoon 3. "

All you need is Team Fortress 2