It's like I need to make a tier list on who is most likely to become my main or something. A large draw to smash is that there's so many characters that I love to play (and fight).
The likeliest of the 3 newcomers and returning vets would be the following:
A Tier: Ridley - A lot of the reasons why I love Meta Knight can be applied to Ridley. Recurring rival to the protagonist, they are both intelligent enough to lead an space army, both are the fastest of the bosses in their games and can overwhelm you with their speed, they both have bat/dragon wings which is a big plus for me. Of course, while he is not "too big", he's not going to be small. And usually characters are big are going to be slow, which is the biggest concern I have about Ridley. I'm not even concerned about being combo food cause of using Meta Knight and Samus a lot. Though I am really liking the tail spike impale move. 50% is nothing to sneeze at even if it can be hard to land. I like having a reason for the opponent to be intimidated. Hopefully that will be enough to rival Samus's fully charged charge shot in terms of intimidation.
A Tier: Wolf - I loved his gameplay so much in Brawl, but didn't really have a good chance to practice it against anyone. I don't love the character as much as I used to though, but only because I only have one star fox game and I haven't played it in a while.
B Tier: Inkling - I got a group of friends that play a ton of inkling so I'll have to get used to it. Though from what I've seen they look like they have a fun moveset.
As for characters already in smash 4. Just saying these are the ones I'd be interested in trying again. After all, changes are bound to happen to characters and change up how they are. Could even make a new playstyle that way. S tier requires a character to be one I love a ton, and to have fun and interesting gameplay to me. A tier just requires good gameplay and liking the character at least a little bit. B tier is usually one or the other. Anything bellow B tier is probably someone I'd never use in a competitive setting (but I may still use a lot for playing for fun, Like Little Mac or Ganondorf for example).
S tier: Meta Knight, Lucario
A tier: Sheik, Cloud, Marth, Samus, All 3 Links for different reasons, Mii Fighters (Let me play online this time please!)
B tier: Fox, Falco, Robin, Captain Falcon, Shulk, Ryu, Snake, Corrin, Zero Suit Samus
C or lower not worth mentioning.
Safe to say it's pretty hard to choose a main.