I think this boils down to an ultimately unenlightening language game, though it may take some thought to conclude as much.
Suppose we restrict perfection to things that exist. Suppose that we now knock over a glass of milk on the floor and have milk and broken glass all over the floor. This state of affairs is then "perfect" because although there was a glass with milk in a preferred configuration a little while ago, there is not any more; and although there are other glasses and there is other milk (and milk in glasses), those glasses are not this glass. So our broken glass and spilled milk all over the floor is perfect.
But what have we gained beyond simply saying that the broken glass and milk all over the floor exists? Pretty much nothing. The point of language is to communicate, and we have taken a colloquial concept of "perfect" and turned it into a meaningless identifier that is synonymous with existence.
Let's not do that. There are better ways to use language.
So, no, our existence is not perfect since, for instance, we can imagine an existence without influenza which would be superior and completely consistent with physical laws (though not the entire history of life on earth). At least, if we use the word "perfect" in this way, it will facilitate communication about such concepts. (Relevant if, for instance, we manage to eradicate influenza as we have smallpox.)
You might then say: aha! But I didn't mean to allow possible existences when I said "existence". I meant to say this unique existence only or the state of existence instead of non-existence so all this talk of non-influenza is silly. In that case, the problem is appling discriminating modifiers to a unique entity. The unique me-how-I-am-right-now is the best, worst, fastest, slowest, silliest, utterly perfect, completely imperfect etc. etc. me-how-I-am-right-now.
Again, this is, upon reflection, just playing an unhelpful language game. Yes, of course, if your set contains a single element, for any ordering
O, that element is an upper bound for
O. Unless you are trying to be deliberately confusing, however, it is better to simply refrain from using language that implies multiple options when there is only one. In particular, when one uses the word "perfect" and "existence" together, the implication is that possible existences may be considered.