When I was in science - the 'holy tenet' is that nothing - even scientific 'fact' - is
"truth". Even a theory that is apparently proven, such as the structure of DNA, or the function of genes, or the fact that oxygen is necessary for human life, is only a theory that appears to be confirmed. Nobody truly profits from considering something
absolutely explained, beyond all further study or doubt. Therefore, we don't. We call it 'fact' if it appears to be so, but all that really means is that
it appears to be so, and in experimental terms, that is enough to be able to conduct further experiments based on that understanding. But theories can be expanded, even made defunct by subsequent studies. Quantum mechanics was the spanner in the works for all those people who thought that Newtonian Physics had explained the Universe and everything in it.
So then, it's the best course to acknowledge what seems to be so, but not to the point of cultivating ignorance of other possibilities. There will always be more to learn for the non-omnipotent being.
Anyhow... what is it you are asking exactly? whether Trish is inferior because she is a demon? That we automatically consider Dante and humans superior? Do we? Since the game's audience is human I'd expect a certain human bias there, but it's not like the fact that (within the game's Universe) demons aren't superior in other ways. They are superior in strength apparently, for example.
Like with any notion of 'inferior' and 'superior' what really matters is context. Survival of the fittest means "survival of the best adapted for a very particular environment/context". If what you want is
power, or a world based on acquisition by strength, then demons are superior beings, because they have greater physical prowess and are probably selfish enough not to let anything stand in their way of getting it. If what you want is
compassion, and believe that would make for a better world, they are (generally) inferior, because they don't appear to have feelings for others. I can't consider demons inferior to humans generally because in the natural order of things a balance between selfishness and compassion is necessary. For humans there are times when we have to be selfish, and times when we shouldn't be, and when altruism and co-operation actually makes us stronger. So I guess otherwise it depends on your own sensibilities whether one is better than another. From Mundus' perspective, Trish was inferior, she didn't complete the purpose he created her for, and was weak-minded in that respect... but from the perspective of Dante, and humans, she's not inferior because despite being a demon, she mirrors him in his ability to care about things other than herself. As a result, she and Dante became a combined stronger force and defeated Mundus. But again, what she is or isn't is determined by which side you are on and what you are trying to achieve.
It's all context, IMO. In the real world humans have their values and their morals, and within our society, compassion and altruism is a good thing, it makes our living conditions better. But also, outside the human experience is the dog-eat-dog world of nature, where only the strongest survive. I would say it would be foolish to disregard either of them, or consider one more disposable than another because we live in both worlds.
Ultimately, I think what Dante does (protect the weak) is a very human perspective, and I prefer it to the idea of humans at the mercy of oppressive demons, as DMC1's intro implies it was. Because compassion is... pleasant. It's good to live in a world where people aren't at each other's throats and there's some semblance of decency, even if it might only be semblance sometimes. So I'll go ahead and say that Dante and Trish are superior beings because the world they want is preferable (to me) to the world a demon would create. Nature created the selfish world, humans have created a world that works within it, but that doesn't have to be violent and ruthless all the time. I believe that what mankind has tried/is trying to create is in that way 'superior' - it has required conscious and constant effort by humans to maintain and progress, rather than the automatic, logical selection process that Nature employs to survive the changing environment. I say that simply because I like a challenge, and I do everything the 'hard way' too.