This isn't a simple yes or no question. E.g. I've been playing the Pokémon franchise for years now and I can honestly say I have never cared about the graphics because the gameplay offers everything I want. Sure good or better graphics would be nice, but they're not essential.
However, on a game like Call of Duty, or in fact, any game on the Xbox 360/PS3, I expect the finest graphics available. After all, when you design a console to be hooked up to at least a 26" TV, you should design games that look fantastic. And there's no excuse for sloppy graphics in this day and age when that's all a game has going for it. If a game's gonna suck, it should at least look extremely good while it sucks.