The 2000s were a super experimental decade in gaming, technology allowed for things that were never possible before but budgets hadn't yet ballooned to the heights of the last two console generations, so devs could get away with taking more risks as long as their cash cows kept providing. Add to that the rise of the casual and semi-casual game, and the creation of new input methods like touchscreens and motion control, and you have a huge variety in the games that came out in terms of genre, style, gameplay, and characters. As far as Smash goes, that's unfortunately a very untapped well, which is a shame especially given Ultimate's penchant for unique, gimmicky and different characters.