Graphics draws my attention at first contact with the game. Doesn't matter if they're realistic, cartoon, 8bit, etc etc. The factors involved are many, and very complex because they are very personal. What i find cute and nice other may find outdated and ugly.
Everything that comes after , game mechanics , history and synergy between graphics and gameplay holds my attention. So i think you just can't analyze a game by separated aspects since they merge one with the other.
This.
What is the first thing you see, when you start playing a game? The graphics, of course. They get your attention and give you a first impression of what to expect. Then it's up to the gameplay to hold your attention and keep you interested.
Overall, both are needed and must be balanced carefully. If either of them are lacking the game as a whole will lose appeal. But as long as the gameplay is fun and understandable, and the graphics are coherent and consistent, then the result will be a reasonably well made game.
Also, other factors like audio, level design, story and that sort of stuff factor in just as much as gameplay and art, but this thread's only asking about those two.