I'm not exactly sure what you're trying to assert by this. Neither Mario, Sonic, or Micky Mouse were called by the same name when they made their debut... what are you saying that indicates?
If you're stating this as solely your opinion, I'm wondering if you want me to not respond to it as a result...?
I will say that though Sonic is given more individuality as a character from his personality and his relationship with the others, but I think that's apples to oranges compared to Mario. Mario says nothing. Who he is and what he's thinking at all times (except in that AWFUL cartoon) are entirely dependent on who's playing the game.
When I play a Mario game, he seems to always be talking trash and marveling at how stupidly cartoonish everything in the game is. If someone else were to play, he could be entirely different. I would argue that Mario would
lose a lot of character if he were more like Sonic simply because of how he is understood by everybody. I'm sure that if he suddenly spoke, a lot of people would go "that's not what I thought Mario would have said..." If you've ever watched someone else play a Mario game and narrate, it's usually pretty apparent that they approach who the main character is very differently.
Example.