SSBM veteran here (5+ years playing, been to dozens of tournaments).
Is it the best Smash game? Yes, by far.
Is it the best fighting game? Debatable, many think it is.
Is it the best game ever created? No, sorry.
The truth of the matter is you simply can't judge a game solely on its technical requirements or skill curve. It's challenging to even compare games that are different genres. How would you compare SSBM to Halo 3? There's so many different components and aspects and playstyles that you'd be really hard pressed to do so. Not to mention each person's standards for what constitutes a perfect game are vastly different.
Melee receives so much praise for a few reasons. Mainly due to the fact that it was NOT designed to be played on any kind of competitive level -- in fact it was supposed to be the opposite -- yet the fanbase has pushed the game's incredibly detailed and precise mechanics to the point of almost making it another game entirely. It also has one of the arguably best casts in any fighting game ever spawned. What other fighter covers such a broad spectrum of characters, games and even genres? A lot of people also love to point out that the Melee scene is as big as it has ever been in history right now (with millions of players and several annual tournaments featuring sponsored teams and awarding large cash prizes) even though it started as a relatively obscure game for the Nintendo Gamecube back in 2001.
The game is really a kind of beautiful accident and I've never had the pleasure of experiencing a more friendly, accepting and dedicated fanbase of ANYTHING. Have you seen the Smash Documentary?