A LOT. first off, pikachu is not the main character, I would say that's either ash or red. but then you're also missing: fzero, chibi robo, punch out!, splatoon, Kid icarus, fire emblem, game & watch, pikmin, star fox, xenoblade, mother/earthbound, and wii series (which should replace Miitopia, which is not a series). Some smaller ones include boxboy, Golden sun, advance wars, pushmo, and star tropics
Mega Man is from Capcom, Sonic from Sega, and some choices are kinda dubious for this kind of quizzes (Miitopia, Animal Crossing). And of course, R.O.B. isn't a "series" at all. Among the hundreds of iconic Nintendo series, why did you choose these ones in particular...?
Updated, sorry. I don't play that much Nintendo, so I was going off the games I had played. That is also why I asked for more games, because I do not know very many.
*** being the main character for pokemon is subjective, you do you but in my opinion it should be red, gold, or any of the cannon playable characters like rosa or calem