My first Smash was Brawl, and I got it back in '08 shortly after I got my Wii and Mario Party 8. I got it because it had Mario and Pikachu on the front, didn't really care about anyone else. Now, being about 9 at the time, I didn't fully appreciate everything the game had to offer. I religiously played a terrible Mario, and my brother, who really likes Luigi played as Mario's green alt because we could never beat Ness after a versus match. (Yeah, we really sucked)
Shortly after getting internet access (this was about one and a half years later, mind you) I began a grand hunt for Gamecube games, after coming to the sudden realization that the Wii could play them. Among the games I bought, Melee was one of them. Unfortunately, I thought Melee was severely lacking in comparison to Brawl, and my 10 year old mind missed the fancy CG cutscenes. To this day Melee is my least played Smash. Not because I don't like it, but the fact that my brother was my only opponent bored me greatly.
Finally, I purchased 64 on the Wii Virtual Console. And I have to say, 64 just has a charm to it that I really like. Though I don't play it as much as I'd like to, it was the first Smash I unlocked all the characters on. (Though that's not really saying much)
Over the years I got better (not good, but better) I unlocked everyone in Brawl, found a love in Lucas because Brawl Mario is... not the best iteration of the character, to say the least.
And now, at the ripe old age of 15, I can proudly say I bought a Smash game at launch, largely in part to my birthday being October 3rd, but whatever. And can proudly say I am 'decent'. I have returned to Mario in Sm4sh due to Lucas' absence.
TL:DR I sucked at Smash, sucked at Smash a bit more, got slightly better, found a main, had him ripped from my cold dead hands, and returned to Mario.