Omaha: pocket aces always the nuts?

Preflop, in Omaha (not hi/lo), are pocket aces (2 aces exactly -- not more than 2 -- obviously AAAA is not that good) always better than 50% to win vs. any other hand that doesn't contain a pair of aces?

If not, what is the worst % a hand with two aces can have preflop, and what are the best opposing hands?

Is this going to turn out to be spam also?

for sure