I'm a devotee of the Cult of Gameplay. Right now I'm finishing up the original Baldur's Gate; before that, I was spending my game time on the original X-COM. Not exactly graphical powerhouses, you know?
Awesome graphics are rarely necessary, and rarely justified. But when they're justified, wow, hold on.
Consider Company of Heroes; a terrific game, probably the best RTS I've ever played, made possible to a great extent by its awesome graphics. (Unit voices by Lee Emery helped, too.) Was it more fun than X-COM? Eh.... Yes, I think so.