The problem with this argument is that
- Shonen Jump/ J-Star all star games are mostly Japan exclusive.
- Jump all star are mediocre games
- Practically no one cares about these games over here in the west unlike Smash.
It would be a huge waste to not have Goku in Smash since he's well known and beloved worldwide and he fits in the game.
The one I listed was released in the West, and I think most people not caring about it isn't that big of a deal since at least it's still available for people to enjoy, as for it being mediocre well not much to say about that.