[Grumpy Old Fart]

Quite difficult to put these in order as they are all important aspects of a game and all are needed to produce a quality game. Here's my order

Gameplay
Graphics
Story

I think the gameplay is the most important out of the three. No matter how pretty a game is if it has crap enemy AI, poor frame rate issues, dull & repetative gameplay, poor controls, poor and pointless puzzless, terrible collision detection, bad camera positioning/angles etc then it doesn't matter how fantastic the game looks you won't play it for more than a few minutes before returning it to the shop you bought it from.

As I said though all are important to making a great game.