He's definetly not a bad addition at all. A lot of people prefer other characters such as myself, but I'll be the first one to admit that he has definetly earned a spot in this game. I am fine with little Mac and pacman being added, they are fine and have quite the following. Mii on the other hand I really could do without but I can handle it, I'm sure they will still be entertaining to play as.
But I totally agree, people who don't think pacman has earned his spot into the game need a reality check. He probably be the second most wanted third party regardless of whether namco was helping with the game or not.
For one thing we do not know sakurais policies on third parties at all, it could be the case that neither snake or sonic were even considered for this game due to them being the guests of the previous game. Other than that there have been reports of sakurai limiting third parties, and pacman sonic and of course megaman all seem more likely than snake. Them adding 4 third parties seems unlikely at this point. Past that it seems that the game has a more Juvenile aspect to it, and snake is a character for mature audiences, he never really fit with brawls cast and he would fit in even less in this game. Lastly, third party status aside, he still seems to be one of the more likely characters to get cut if sakurai needs room for newcomers.