I've been using Mario and Sheik for MUs that I don't feel comfortable as Bowser in, but I have been looking for a character I'd want to main in place of Bowser. I really do feel as though I'm reaching a roadblock with him, and it sucks because the game's only been out for a year, whereas I didn't feel this way in Brawl until my fifth year of using him. The game is simpler, yes, but there has to be something we're not seeing with this character, right? I wouldn't put serious thought into a character change until 2016.
As far as that goes, I'm running into two issues: switching to a new character would require me to play the game more if it's someone completely new. I only play Smash 4 at tournaments and maybe practice movement occasionally.
The other issue is the same as what happened in Brawl. Bowser is WAY too unique of a character. No one has all of his tools or quirks, so I know I wouldn't feel as comfortable with anyone else.
So then I get stuck in this cycle where I either go all Bowser and occasionally use Mario or Sheik for ease of use. I've thought about Ryu and Ike really, and then some off-the-wall **** like Mega Man or Greninja because they just seem cool. I just don't know.
I don't know who's the closest fundamentally to Bowser, and I know for a fact that I can never actually drop Bowser lol
edit: I'm done lurking. As an update, I've done pretty well in my sub-region where my college is at. I haven't gotten worse than 3rd...A LOT of 2nd place finishes though. ZSS is an e x t r e m e l y stupid character.