Ok, so I'm going to actually attempt this now... For me a AAA game is a game that's trying to convey a complete reality. If you look at the scope of video game evolution, it has really started with pixels themselves, and evolved to pixels that form 'nouns' that we're actually familiar with like cars, people, guns, etc. To me, a non-AAA game is something that restrains its attempt to convey a whole reality for the sake of game mechanics. Something like Tetris or even Mario, the later of which just sort of uses psychedelic imagery in a generalized way. While these games can be fun, and even more pleasurable than "reality" games, they're not attempting to completely suspend our disbelief. So, I think the theory of AAA games, is that we don't just play to exercise fun mechanics, but to believe we're in (a)nother world. We sacrifice mechanics to some extent, to exploit technology and use stimuli that makes an experience virtual.
I guess I'll also add, I think the standard to which we hold a game's success in conveying a "complete reality" depends on the technology available to the developers on their game's platform. So, you can argue that a game is or isn't AAA on the PC, Wii, or iphone.
Also, I do think different traditional game genres fall into the AAA fold---ie even though racing games don't even show you the person driving for instance, because the mechanics are only driving, it can be considered AAA. However, I think those kinds of "focused experiences' status is conditional based on how much they exploit the technology. So, Mario Kart may be more fun than Gran Turismo, but it's not AAA because its merely exploiting the idea of racing to create a sense of "fun."