What are you talking about? Nobody gives a damn about Donkey Kong? Or Kirby? Or what are you talking about? PSASBR included so well-known IPs like Ape Escape, Starhawk, Sly Cooper or Fat Princess. So fair to the par to games like Earthbound and Ice Climbers.
And Sony had no problem to include Kratos and Nathan Drake in PSASBR, so these aren't cartoony at all, so seemingly that is no problem.
After all Smash Brawl had 39 playable characters and four years later PSASBR only included 24 characters, even including DLC. Two years later Smash 4 included 51 characters and 7 DLC-characters.
So yeah, Sony has much more difficulties to whip up recognizable characters from different IPs than Nintendo.
You're really reaching with this. Going out of your way to tilt the playing field doesn't make your comparison look better. I don't see the point in doing that.
It's obvious that the developers for PSASBR were looking to start small enough to leave room open for future games. Something pretty much all fighting game developers do--including those for Smash. But you're comparing PSASBR to Smash sequels? To the fourth game in the series?
Add to that my previous point that many current Smash characters are from the same series of games and it looks to me like you're really exaggerating the difference.