A_man13
Smash Master
Thought I'd contribute before all of the good topics were taken up. 
Certainly there are tons of good Mario games, but there are certain levels in the platformers, courses in the Mario Kart franchise, and even a few arenas from the sports games that just make you go "Wow, that was Awesome" every time you play it. A LOT of the galaxy designs did it for me just out of the craziness and off the wall level design each planetary path had. Another personal favorite of mine is the Whoa Zone from SPM for the same reasons I like galaxies levels; it is pure pandemonium to navagate, but it is all rewarded by a very unique old school side scrolling galaga-like shooter boss. I'm pretty sure I'm not the only person who has a favorite level, so the question arises; what is your favorite level in a Mario game?

Certainly there are tons of good Mario games, but there are certain levels in the platformers, courses in the Mario Kart franchise, and even a few arenas from the sports games that just make you go "Wow, that was Awesome" every time you play it. A LOT of the galaxy designs did it for me just out of the craziness and off the wall level design each planetary path had. Another personal favorite of mine is the Whoa Zone from SPM for the same reasons I like galaxies levels; it is pure pandemonium to navagate, but it is all rewarded by a very unique old school side scrolling galaga-like shooter boss. I'm pretty sure I'm not the only person who has a favorite level, so the question arises; what is your favorite level in a Mario game?