As everyone else has already said, I tend to favour gameplay more than graphics.
However, a series I've never played any of with a new release is far more likely to drag me in with spectacular (and I mean truly breathtaking, not necessarily realistic) views than with fairly standard graphics. This can be outweighed if I've heard favourable reviews of the game itself or its series or developers but generally, it's snazzy eyecandy that most violently grabs my attention, after, of course, an original plotline.
However, a series I've never played any of with a new release is far more likely to drag me in with spectacular (and I mean truly breathtaking, not necessarily realistic) views than with fairly standard graphics. This can be outweighed if I've heard favourable reviews of the game itself or its series or developers but generally, it's snazzy eyecandy that most violently grabs my attention, after, of course, an original plotline.