Personally, the only overrated AAA game I've played all year (on any platform) is GTAIV.
It deserves AAA status, it's just not the best game of all time (uptil now).
But I must say, more often than not, I agree with the "AAA" status system, whether that be because I get influenced by the status and more often than not, like games without it less, I don't know, but I find that if a game has gotten an average of 90% or more on granks/metacritic, I will enjoy it or at least appreciate the game.
Incidently, my 2 favourite games of all time have not been "AAA" games (KH and FF8 for those interested).
So I guess what I'm trying to say is, I can see why certain games achieve AAA status, because they are easily likeable to everyone and they are games anyone can appreciate on some level, but I wouldn't denote "AAA" as being a measure of "fun" though.