I don't own the new Smash (because I don't own a Wii-U. *insert sad face here*). I've played all of the Smash titles, though, and even won a pretty "big deal" tourney for Brawl.
All of that being said, I have two mains: my "For Fun" main is Bowser...who, more or less, winds up being all I play BECAUSE HE'S JUST SO MUCH FUN TO PLAY. My "For Serious" main is Mr. Game & Watch, although I don't really enjoy using him in Brawl or Wii-U Smash as much as I did in Melee. I pick him when I absolutely MUST win, but he's not too fun to use...
...UNLIKE BOWSER!!! =P