Cart condition is important to me, but I won't be anal about it. As long as the game is in good condition, I don't mind. Not beat the hell out of and I am ok. I have carts that have been ultra worn, but they still look good, so it's fine with me. Nevertheless, I try my best to get the best condition possible and will skip over games that either are "loose" or look like shit.
From 1 to 10, 10 being best, the most I've accepted is a 5, or just "fair". Not too bad, not great either...just "OK" or "fair".