The only argument you've brought to argue against the 2D style is that because the characters are from 3D games they shouldn't be in a 2D crossover. What's wrong with 2D exactly. If your answer is the same as always like "It doesn't make sense since the games are from 3D games" then I don't know what else to tell you lol.
2D is great for fighting games, and it works with PlayStation characters. I'm willing to bet a majority of people will agree on that. Never said that 3D was wrong for a crossover for this game, just if it ain't broke don't fix it.
And lastly it doesn't give automatically give them more creativaty, that's an arbritary thing to say.
Except that's not what I said at all. You still don't get it, do you? 3D games are what the PlayStation mainly focuses on and this game is suppose to be a tribute to PlayStation, so obviously being a 3D game makes more sense. Nobody can really argue otherwise.
3D is great for fighting games too and there are many fans of 3D fighting games. Heck, there are some people who like Power Stone more than Smash Bros. so it's not like using Power Stone's style would be a bad idea. Also, as much as I liked PlayStation All-Stars, it definitely did need fixing concept wise. It was a different game from Smash Bros. but still bared such a strong resemblance to it that it didn't give off that impression and that's why fans still calls it a "Smash clone" or "Smash ripoff", an image I'm sure they didn't want. Had they used Power Stone's 3D style (which also happens to fit them better), none of that would have happened.
I'm not trying to force you to change your opinion. If you want it to stay 2D, fine but it's really not hard to understand why it makes more sense to be a 3D game if you're really a long time PlayStation fan.