A penis that is too long can cause cervical bruising, one of the single most unpleasant experiences (I am told) that a woman can go through. Also, it can apparently be very uncomfortable. My female friends share too much sometimes.
Anywho.
I think a game could be too long, but I have yet to find one that is too long for me. I was raised on FFIX, so for me a sixty hour game is nothing. I still enjoy shorter games very much, but I've never gotten bored with one.
That said, it's just the old different strokes argument, some people will only play long games, some people prefer short games. If you're someone who plays and likes games with only six hour campaigns but endless replay value or a good multiplayer or whatever, there's nothing wrong with you, and for someone like that a 30 hour Mass Effect-a-thon would probably be boring and samey.
So yes, games can be too long for certain, just like games can be too short for certain people.