"but they lack lasting power once you stop playing."
This sounds like a good litmus test for me. If you're still thinking about a game many months after you finish it, then it's probably something more than a mere diversion. In this sense, perhaps, the best game reviews should be retrospective, rather than reactionary on the day of release.
This is the essential difference between amusement and art for me. I may have read Fahrenheit 451 years ago but it altered the way I think. It gave me new faculties for relating to and judging new experiences and ideas.
The closest a game has come to that mind-altering experience is Go. I've heard myself relate to and judge new ideas through Go when I say, "... like in Go..." Or I generate new ideas and ways to express myself by using concepts developed while playing Go.
We might hear things like, "Life is like that grind in World of Warcraft except it ends," become common place some day... except with some more culturally-relevant analog of some future incarnation of what we call an MMO.
But video games are just so darn young as a medium of expression that I don't think we've reached that level yet.
This sounds like a good litmus test for me. If you're still thinking about a game many months after you finish it, then it's probably something more than a mere diversion. In this sense, perhaps, the best game reviews should be retrospective, rather than reactionary on the day of release.