I have never got into this game competitively, but I have been the best of anyone that I play besides my brother.
N64, I was still pretty little, and I pretty much only used Link. I was good considering how young I was.
Melee was very fun. I started getting a bit better at SSB, using several characters. I used Falco, Fox, Roy, Link, I wanted to use Mewtwo, but he just wasn't that good in my opinion.
Brawl had good potential as a game, but it did not really use it well. I started getting much more skillful than I used to be. All of my friends would say how annoying it is when people used Ike (which I never did, mainly because I couldn't pull it off) because he was too good, to which I would say "then just use him yourself", and then they had no good response but they were still angry. Anyway, after some exploration of the new characters, I started just using Wolf. Wolf is not popular, but I love doing that thing where you shield and move away at the same time (I know no competitive jargon) and then using the side + A, which seems to annoy people.