@ Chaos
The only thing any character represents in smash bros in themselves. Nobody wants "filler" characters just to "represent" something.
@ Habanero
Well, 549 Pokémon "sounds like too much." And selling what=??? 200 million video games, getting millions of views for hundreds of TV episodes, and making billions off a card game "sounds like too much." But that is what Pokémon does, and has been doing for 16 years. And Pokémon keeps getting more and more popular. Thus, that is why so many people want so many different Pokémon to be playable (or Pokéball Pokémon and whatnot) in smash, and why so many Pokémon potential newcomers are ridiculously popular.
There are so many Pokémon, and lots of good choices. Like I said, we got 549 choices of them, all of which are in each game. With games like Mario, Zelda, and Donkey Kong, you can't even say that characters like Luigi, Ganondorf, or K. Rool will be in them!
Also, it's not like Sakurai sits there with a calculator going "Hmm, well if I do my equation by the calculus squared of the trimester of the rectangle of the roster, 7 playable characters from Pokémon universe seems to be obsolete." What Sakurai does instead is merely add characters that are important to their series, that originated in gaming, that perhaps or popular (this isn't a requirement), that may be forgotten yet important (this isn't a requirement) that make us want to play the game (to where we'll pay money for the game!), that balance out the rest of the roster, and that add something new to smash bros.