Tell me good and addictive game

Hello, and for first, I am sorry for my bad english.

So, I want some good and addictive game. Not any MMORPG:s or other only-multiplayer games. I want just some First Person Shooters with levelsystem, or buyable weapons, or Top-Down Alienshooters, where I can buy weapons and get levels. Games like Fallout, or Alien Shooter 2. RTS-games etc. are good, you can tell me them too, if its just addictive and it has rewarding gameplay, like levels etc. It have to be for PC, and it can be shareware. Red Faction: Guerilla is one game that I love, and games like that you can tell me, but its for Xbox 360 or PS3.

Not a shooting game but with many upgradables prototype is very addictive game to me...

S.T.A.L.K.E.R: Shadow of Chernobyl perhaps? It's a singleplayer focused FPS with RPG elements.

Try Deus Ex.

For rts try Dawn of Discovery very addictive city builder well it was from the demo and i was suprised how much i liked it

Deus Ex

Tron 2.0

Rise of the Argonauts

Hellgate: London

Call Of Duty 4 And Prototype.