Actually, the more important arguments in favor of Rainbow Cruise is:
*Super Mario 64 stage
*returned in Brawl
So obviously, there are a good deal of people that like Rainbow Cruise, if it managed to return in a later installment. Plus, Super Mario 64 is the VERY first Mario game in 3D, so that game is in a big need of a representation (too bad Rainbow Cruise is gone in Smash 4).