Truly depends on the game, some are a CHORE to replay (any game with unskippable cutscenes, for example!). I've recently replayed games a lot. I got 4 characters to Lv50 in Borderlands 2, which is 4 regular playthroughs and 4 True Vault Hunter Mode playthroughs. Oh yeah, I also had a 2nd Gunzerker but I only finished the first playthrough with that one and I was playing through it again with the Mechromancer but I decided to stop until they release the current hot fixes as a proper patch.
I also replayed the hell out of Metal Gear Rising: Revengeance. Even when it wasn't a full replay, I replayed some chapters a lot for the heck of it. Super fun game, insane replay value.