Wow, what the hell happened in this thread? It's like a goddamn pile up.
From reading this thread there are a lot of obvious things to me. First is that most people passing judgment haven't even played the game. Second those who have played the game VERY CLEARLY have not unlocked Title Defense mode. While you may fight the same 13 guys again, they are COMPLETELY different. They could've skinned them all with a different appearance and called them something else and people would have no problem believing they were a unique character.
People are also glazing over some of the other stuff the game has in store, such as the awesome Exhibition mode. All of the challenges there are ALSO like fighting a new boxer, since you need to approach each battle so differently.
To say that Nintendo didn't put adequate resources on the title and rushed it out the door is fucking nonsense, and actually a slight against this amazing game. So they didn't include a bunch of new guys and there aren't 15,000 different boxers to fight, big deal. What is here adds up to MANY hours of gameplay and is extremely fun.
It seems to me that they put in what they felt was adequate to make for a complete gaming experience and polished it all up to the point of near perfection. And maybe, just maybe, if the game sells well they are planning on making a sequel with some of the neglected characters and adding a slew of new ones.