It has its own distinct competitive scene. From what I understand, the generally-accepted top players of each game would be considered to be
64: Isai
Melee: Armada
Brawl: Mew2King
Smash 4: ZeRo
Project M: Junebug
However, Mew2King is also top 6 in Melee, top 20 in Smash 4, has strong showings in PM, and is pretty good at 64 as well despite rarely playing it. Overall, he's easily the best player throughout the whole series.
I'm the worst at smash nowadays. Ever since my pro controller broke I had to use a gamepad, lag and other things. It's been like this for awhile now, so I stopped playing, which makes me an ever worse player if I go back to smash 4.
But Smash bros wii u has Ashley costume. Which makes it the best out of the others.
Well Brawl wasn't bad, yeah tripping was a thing but I rarely ever encountered that. Plus we all know that Brawl has the better soundtrack and a theme that DOESN'T PLAY EVERYWHERE.
In all honesty, though, I do have to say that I like Brawl's mechanics a bit better than Smash 4's as a whole. Sure, there's tripping, and you can just air dodge out of combos for free after 8 frames, but the ability to ledgehog makes edgeguarding a much more significant part of the game. Additionally, while Smash 4 does have much stronger combos than Brawl, it also means that losing the neutral is much more costly, which isn't very appealing in a game where movement options are relatively limited and so many actions are easily punishable. I'm also a big fan of the refined meteor cancel mechanics (complete with balancing around the recovery types of each character; wing characters have to wait longer to meteor cancel, and tether characters can do it sooner), which Smash 4 decided to completely remove for some reason. The main complaint I have about Brawl is its character balance, really.
That's what happens when you give a character as many jumps as Kirby, as much range as Marth, two glides, four specials that can be used to recover, and nearly no startup or endlag on his attacks.