The origins of the term AAA in games development is a reference to investment banking terminology whereby a AAA investment is a highly reliable and high margin product. This means that a developer will put a huge amount of resources behind it to maximise profits.
The label AAA is in no way a sign of quality but in fact, a companies way of labelling profitability.
I originally intended to post a concept for a hybrid genre sci-fi game (Like ME meets SF/SC2  + Elite) but as long as the financiers to publishers see that it is comparatively less risky to re-use a Gears of War type "game production recipe" because of the linear/predictable/simpler to test nature of these sort of games in comparison to more open world games, why bother.
It can be surmised that Halo as an "AAA" title was too risky for Microsoft. Now they are looking to produce a more safer, even more linear and predictable shooter. I'm predicting this will eventually boil down to an "AAAAA"-rate game with a single "Click to Win" button for some easy instant satisfaction. When that happens, I'm going to bring out my "Electronic Farts" app, which makes sounds when you press the "EF" logo.