Personally i think the whole AAA/hyped game thing is a bit of both arguments. The simple fact is that there are 2 distinct game types, those you hear plenty about years before launch and that run looooooong PR campaigns to pump up fans, and those that pop up in review month and are on the shelves before you know whats what.
Now the former are mostly classed as triple A titles correct? So now look to 'why' they are so branded. The main reasons are either media hype or corporate/PR hype. The end result is the same (games branded AAA) but often the two are confused. Lets take a game like Oblivion, now although there was reasonable PR hype around this game, most of the hype and speculation came from the media thanks to the early screens that seemed to defy reality in terms of scope and quality. This media-centric hype built up the game in the public conciousness, not because money was particularily thrown at plugging it, but because it grabbed attention, in the case of oblivion with its visuals.
Now take Gears of War, as a new IP and as a landmark title for the 360, this had money poured into PR and it was really money that had 'Emergence Day' on everyones lips, i for one knew next to nothing about the actual game until just before launch, it was a true PR AAA in my mind.
So whats my point? My point is that most good games are AAA titles because of one of these reasons, so while 90% of good games are AAA before launch more like 60-70% of triple A titles turn out to be good games. A percentage are picked up on merit and a percentage on PR budget. Thus AAA is a valid category imo but you will always get your flops and sucesses because the foundations of the category are so varied.