Really can't say that I've ever had this "problem". Closest thing I can think of was my situation with Resident Evil 5. A friend had rented and one weekend later we had beaten it. There was still more to do, get infinite ammo and such, try out the multiplayer...so I decided to go ahead and buy it, thinking that it could turn into the type of game that I'll just randomly get the urge to play through every now and then.
Well that urge never came. Think I played through it three more times (the last time was just having fun with the infinite ammo rocket launcher) and then I moved on to something else. Never touched it again, never tried out the multiplayer. I'd catch myself looking at the case, trying to will myself to want to play it again, but I just had no desire to do so. Eventually it got traded in to help pay for Black Ops, I believe.
Well that urge never came. Think I played through it three more times (the last time was just having fun with the infinite ammo rocket launcher) and then I moved on to something else. Never touched it again, never tried out the multiplayer. I'd catch myself looking at the case, trying to will myself to want to play it again, but I just had no desire to do so. Eventually it got traded in to help pay for Black Ops, I believe.