I'm not even sure what fits into what category. I'm mainly into MMOs and when I think about graphics I don't even know what that includes. I mean you can have a pretty cool world design with weak shaders and effects. As for game play and story, you would think those would be #1 and #2, but then I remember EverQuest and the game play was so so. As for the story, few people actually did the quests, especially at the lower levels. It even got the nickname NeverQuest. Yet I still found it fun to play for whatever reason.
That being said, since I'm working on an MMO I decided to try to prioritize this. I split it into 4 categories however.
1) World design
2) Game play
3) Graphics
4) Story
I prioritize in that order. The reason I put story last for MMOs, is I find most people don't really care that much. I mean they may go though the motions but really a player's personal story is driven by player to player interactions and so the built in story line doesn't matter that much. On the other hand I think a kind of underlying environment/story is important. Different races, different regions, stuff like that. However I kind of think that goes more into world design.