I think a super smash bros movie could actually be pretty good, just as long as they don’t turn it into a nintendo cinematic universe or something. Maybe have the mario characters as they appear in the animated movie and the pokemon as they appear in the anime (I don’t really think detective pikachu would work) or even sonic as he appears in the movies if they want to include him but that’s it and making movies for every IP included would be a pretty bad idea.
Crash Bandicoot has dark lore and between-game character development; Mario has fought god-like threats and pulled off beyond-imagination feats; Pac-Man has been welling to delve into darker locales and tones from time to time. I don't know what makes Kirby so special.