In terms of importance, i'd probably say originality, challenge, story, gameplay, and lastly replayability are what I like to see. I love a game that pushes me and takes real effort to complete, not something I can halfass and still get from the start to the finish. I don't like to getting myself a lot of new game because if I don't spend enough time with a game, it's just a waste. When i'm looking at getting myself games though, it's usually either the story to the game or some unique approach it has that catches my attention to buy it (things like Nier Automata or Jotun, while something like Just Cause looks like the same game I've played under multiple different titles).
On top of all that, the soundtrack isn't often something I go trying to find before getting a game, but a good one is a great way to captivate me and make me enjoy it significantly more.