I believe the 33% pokerwhiz is talking about is taking the starting aces against all other possible starting combinations from KK down to 72 off, not comparing AA to one, two or N other players hands.
I do not agree with limping aces with 4-5 other players, too many dangerous cheap draws, you may even improve your hand less than the drawing hand improves, make them pay to draw against the rockets. Take the aces against a hand or two and use the math advantage to the fullest by betting with those big boys. If you know there will be no more than 2 others with you to the flop (others have already folded), then the limp may come into play (and hopefully someone else gets brave pre-flop, then you have em) to disguise the strength of the hand.
If you are interested in limping with aces regardless of situation, I suggest a tip I read from Mike Caro (The mad genius) on playing aces. There are 6 combinations of aces, 4 consist of one black and one red ace. The others are the two black or red aces. Limp when your aces are the same color, raise if they are different. You will be raising 2 out of 3 times you have aces thus possibly disguising a little of your rocket play. Personally, I prefer to give more weight to the situation and current playing rivals, but wanted to share the tip.
Thanks pokerwhiz for the insight, just wanted to add my 3 chips worth.
Shuffle up and deal!