According to the book I read, here are the exact statistics on AA winning based on the number of players in the game, based on all cards being played out.
Players % win
2 85%
3 74%
4 64%
6 49%
8 39%
10 31%
As we all know, AA is NOT a sure thing. As for me, over the last few weeks, AA has been very good to me in showdowns, I can only recall losing with them once, in maybe a dozen or so times.