Three words, one number: Half Life 2, Man

I find Civ4 hard to get into. I'm more used to the Total War series of turn based stragety gameplay.

Crysis - This game is truly awesome, great graphics and really fun multiplayer and it is a fun single player experience.

Enemy Territory: Quake Wars - A great multiplayer game with great visuals and not to high of system requirements.

WarCraft III (Get the Battle Chest) - This game really has the best value out of most games out there. The single player through both Reign of Chaos and The Frozen Throne is very in depth both story and gameplay wise and then the multiplayer is tons of fun. Also there are the endless custom maps that offer tons of different gameplay types that can provide hundreds of hours of playing.

StarCraft (Battle Chest) - possibly one of the best RTS games there is. Although it's old it's still worth it and you'll want to practice up for the upcoming release of StarCraft II and so that you aren't behind in the story.

Battlefield 2 - I know you said you want games with a strong single player but this game is a lot of fun online and I would suggest it to any FPS fan.

Doom 3 - Now this is a good single player FPS, you get very drawn in to the atmosphere of the game and the single player lasts at the least 20 hours, and that is excluding the expansion which adds another 12-15 hours. Doom 3 has to be one of my favorite single player experiences ever in a FPS followed closely by Crysis and the game is only $20 now (but another $20 for the expansion). Doom 3s graphics are also still some of the best looking out there despite the game coming out in 2004.

Also I would suggest getting xfire and you can add me as a friend, my sn is ickalanda and I will be sure to help you with any further questions.

Medieval 2: total wars is my pick! put the graphics options on high and you will have the most massive of battles! :D

I had like 4000 people on the battlefields killing eachother in the most thrilling battle today :)

1) Orange Box
2) Orange Box
3) Supreme Commander
4) Bioshock
5) Orange Box

FPS, Strategy, Action strategy, RPG:

Halo

KOTOR

Battlefield 2
Battlefield 2142
anything Call of duty (even the united offensive expansion was good)
Spore (coming soon) Creature creator
Europa Universalis 3
Rome, Medieval: Total war
Roller coaster Tycoon 3
Company of Heroes
Starfleet command (I, II, III)
Emperor: Rise of the middle kingdom
Sid Meier's Pirates!
Black & White

Risk II

Just so you know, you can get Quake Wars for fairly cheap these days.

Don't forget to download FEAR Combat and Wolfenstein Enemy Territory also. They're free.

Also, you must get the Orange Box. You have no choice in this matter.

Wait for Starcraft 2 it'll be the greatest game ever XD

Bioshock is only $15 on Steam this weekend. Be sure to get it before the promotion runs out.

You don't need to buy any games. You have Solitaire and Minesweeper. What more could you want. Spider Solitaire, o wait you get that also. Online checkers, count me in. Hearts Cha-Ching.