Games with good length or replay value

As awesome as i think the Call of Duty games are, the campaigns actually have little replayability for me. Although there are things to keep me coming back, such as Nazi Zombies, Spec Ops, and of course... the insanely addicting multiplayer. I am looking for games that have a lot of replay value, or that last a decent amount of time.I am planning to invest in Medal of Honor and Call of Duty: Black Ops later in the year.

So as you can probably tell, i am a huge shooter fan. But i also can enjoy a few RPGs as long as they are really enjoyable. So suggestions for both are completely welcome :D

Also, if anyone has any ways to ad replayability to games like Call of Duty (the singleplayer portion) please, share that as well :)

RPGs are always the games with the best length and replay-ability. Games like Dragon Age: Origins and The Elder Scrolls: Oblivion you could play for months and not see everything, and this would be months of good solid gameplay not boring grind. If you haven't already you should try RPG games that involve shooting such as Mass Effect 1 and 2, Fallout 3 and other slightly less RPG games like Deus Ex and the STALKER series.

the path

red faction geurilla is fairly large full of replayability

a reckless disregard for gravity (because falling with style NEVER gets old)