gameplay, which I consider a part of which is time it takes to beat a game. If I can beat a game within 1/2 hour I hate it, if it takes a few trys and umteen hours, I consider it a challenge and worth it. This is why I love RPG games like FF and such.
Buy a game for say $50. and beat it within a day, or, same price that takes a few months to beat.
Gameplay all the way, close second is the stroyline(almost equal) because who wants to play a game to have a crappy ending, or being not interested at all.
Graphics, are subjective. Someone might see something and like it while others don't. This I find not relative.