If you actually have educated yourself about the game, you are in as good a position as any to try to predict its success. At least then you're basing it on more than "it sounds generic". I'll point out though that even at that point it's just your own opinion. Like this, watch me go, watch me go:
I don't personally like Smash Bros. At all. I'm not excited about the next installment, which looks just like both games that came before it. I doubt it's going to sell any better than the last one, and it will probably sell worse since it isn't bringing much new to the table that I can see.
At any rate, I'm more or less finished with this discussion. I've already been in too many tard snowball fights on these forums for my liking, I'm not going to get in another one.