There's much, MUCH more to Smash Bros than a competitive experience. Smash Bros is a celebration of Nintendo and it's history. The characters, stages, items, music, trophies, and every other little detail in these games mean a lot to people.
Judging a game like Smash PURELY on its competitive side is ignoring a lot of what makes Smash special.
I think looking at the smash games as "objectively superior or inferior" in comparison to one another is ignorant. They're all different, all offer different experiences, and all mean different things to different people.
For example, if you value single player experiences, then you're going to love brawl, and probably will think its a "superior game" in comparison to Melee.
Nobody is right or wrong, but when you say "Brawl is considered to be inferior", I think you're talking strictly from a competitive point of view, which is by no means objective. Its an opinion.
Believe it or not, some people just do not like how fast Melee is. Some people don't like the physics. They don't like the way it works. Some people prefer the later games. And no matter how much you may BELIEVE Melee is "superior", at the end of the day, that's just the way hardcore Melee fans view things.