Its not like one is guranteed to hit with such an Ultra move just because he has it filled up and ready. I know what you mean with the whole "revenge" concept being akwardly awarding to the "damage receiving" player, but you have to admit, that such a game mechanic makes more sense in a fighting game than, for example, a strategy game.
One of the fighters simply starts getting pissed and with anger comes (sometimes) newfound power.
In a strategy game it would look somehow weird. A whole army starts getting angry and what? Does more damage with their exactly same guns and tanks and stuff, that it did before? Doesn´t make a lot of sense here, if you know what i mean...
So i wouldnt be too harsh on this game mechanic. Ultra´s, well most of them, are hard to utilize correctly anyway. More than 50% of my games never see an ultra move...