I did a quick search and couldn't find anything about this. I'm not looking for the "best" single player game you've ever owned, just the one that you find you can replay many times and still enjoy it. Single Player games only! For me there are two strong contenders, and Half Life 2 just made the cut: Borderlands + DLC Test Drive Unlimited + Megapack Half Life 2 I've played Borderlands and TDU right through somewhere between 5-10 times and will always start with a new profile every few months... each time it's like coming back to a completely new game, and I must say I actually enjoy them more each time. I've had TDU for nearly 5 years LOL.
+1 to Rome Total War. Turn stupid advisor woman off and you're good to go I also would say KotOR as I've played it a lot of times, both sides of the force, different planets in different orders. But now it's getting on and looks quite aged. Edit: kingred, skyrim isn't replayable, you just keep playing.....forever......or until you want to be not a mage lol
Oh, and turn best bit of RTW - leaving your cities in chaos so they must rebel, only for you to have a army of 1000+ to crush them. Oh, is that just me? *hides*
I didn't think Gunsmith would say Crysis Half-Life 2, Portal, Defense Grid, Beyond Good And Evil, Black, any Final Fantasy games. All things i replay on a fairly regular basis.
Total War games, every time. Probably some of those Paradox TBS games too, but I'm not brave enough to try them
Fallout 3 (With mods. Don't hate me) Kotor. Both of them. All of the Homeworld Games. Just because you can use such ridiculous tactics at points to see what'd happen. The Half Life series. All of them. Both Portals. That's about it. More may come to mind, but those are the key ones.