Banjo was an icon of 3D platforming years ago but he's reduced to nothing. But his influence is still felt; we got a half-assed overhyped game (by opinion from most who played it) directly inspired by Banjo, which is Yooka Laylee and it even has all the problems the nostalgic 3D games had back then that everyone forgot about because nostalgia.
Ken was an icon of fighting games back in the arcade days, as Street Fighter is immensely popular and iconic, and it remains relevant today. Ryu and Ken are like Mario and Luigi in Streetfighter Land.
Geno was some Super Mario RPG character that apparently is popular for whatever reason. I know he's been highly requested since the Brawl days.
Mach Rider, eh, I know you don't know.
Chorus Boys are the characters from Rhythm Heaven and were part of "fake" leaks for Smash Bro