With RPGs, I like to replay with different characters. A lot of times the storyline changes some per race or class.It really depends on the game. If it's a sports game, or a fighting game, then of course I replay it. However, there are some games that have little replay value (games that give only a little bit of extras when you finish the game) like some RPGs. After I finish a 50 hour RPG, I normally don't bother to play it again unless the story is really enthralling, or there are multiple endings, etc. so again it really depends on the extras that they put in the game after you finish it.
If there are no incentives to warrant another play-through, I just move on and play another game.