I bet people would have still complained, even though the Aliens would be stronger. I just think people don't like the idea of a predator killing so many Aliens, that's not to say the Aliens were tough and super intelligent because they were dumbed down no question. I think it's hard to keep both fans from each franchise happy (even though most fans like both franchises, everyone has there favorite) and you will end up, upsetting one of the groups. For instance Grid kills two preds, all the pred fans start saying how this would never happen. AVPR, (even though the Aliens were retarded) Wolf kills a bunch of xenos, and for the sake of argument lets say they make these xenos as smart and as tough as the one from Alien, the directors still want to express their idea of this super hunter, so they make wolf kill a bunch of them. The Alien fans become angry, and leave the theatre not liking what they have seen. AVPR had other flaws besides the aliens being pathetic, but I'll leave it at that.
I'm not saying that you can't have a movie where both sides leave the theatre happy with what they've seen. It hasn't happened yet at least not according to the majority of fans. I think the whole concept might be a bit harder to pull off than we all think, but hey they're professionals, they should be able to. Who knows maybe they'll release another AVP movie with awesome moments of both species.