It depends on which Sony characters vs what Nintendo characters, but I'd wager you're right that some of the characters in SSB aren't (weren't?) as popular as some sony ones. But I don't think people will admit it because they're too busy hating it :D

LOL THE HATERS WILL PLAY IT BUT NEVER ADMIT IT. i bet this game will still get negative fan reaction, despite people playing it. I won't be though, obviously. Maybe its just because the haters can yell louder than the people who actually like it. IDK.