Graphics alone? Almost never. If the game is otherwise great, I'll play it. I've got the original X-COM in my laptop drive right now and Might and Magic VI next to it. I prefer for a game to look good for its era, but that's all I expect.
I'm actually less forgiving of bad graphics, especially poor camera position (part of the graphics IMHO) the more recent a game is. There's just no excuse anymore. As an example, the developer's deliberate, malicious choice of the worst camera angles imaginable did a lot to turn me away from the first Resident Evil, and that infernal over-the-shoulder camera didn't help me any in RE4. If it's too dark to see properly or if the creature has cloaking, okay, I'll deal, because it's part of the game. But you do not, repeat do *NOT* include the camera as an enemy if you want me to like your games or your company.