Ace and Aoshi haven't fought head to head (and aren't likely to ever do so again T T), so this can only be done through speculation.

First, from their respective encounters with Akane, Ace should not have been able to beat Aoshi. Ace was almost killed by Akane in seconds, while Aokiji and Akane fought for days before Akane narrowly won, so it's clear that the two of them aren't on par with each other's abilities. So Ace and Aokiji's ability is immediately obvious.

Secondly, after all, Aokiji is the three great generals, Aokiji's overbearing aura can also be seen to be relatively strong, for the comparison of both sides is the natural system, no overbearing aura simply can not fight. Although from Luffy's memories can be speculated that Ace should have a hegemonic color hegemony, but Ace's hegemony and are not practiced at all, he can not control the hegemony at all. So in this regard, Ace can't beat Aoyagi. (I actually like Ace ah ah ah ah ah T T)

So I personally think Ace can't beat Aokiji.