Very unique fighting game but not necessarily better.
Gameplay - the concept is great in theory. Instead of just beating an opponent to death, the player must wear them down enough to either knock them off the stage/arena or knock them off the screen (or into the screen... splat). However, that works both ways and the AI can get tactically cheap, even on Very Easy. Not to mention the mass confusion caused by the plethora of motion on-screen, especially with 4 characters involved. The camera zooms out to accomodate but hinders the view of the action. More often than not, i discovered that i've been muscled off the the edge and didn't even realize until the immense explosion tower emanates from wherever my character's corpse ended up. Even the option to display a name above my character doesn't aid in keeping track of him/her.
The controls take a lot of getting used to. As with most fighting games, you must learn each character's moves/strengths/weaknesses & choose whichever suits your playing style (or just learn a new playing style). With SSBM, you also have to learn how to save yourself from careening off the edges. There's double-jumping (or floating or flying), then each character has a special that can launch them in whichever direction you choose. But some can go further than others, which puts certain characters at a significant disadvantage.
Also not sure why they bothered utilizing the pressure sensitivity of the Gamecube controller. It's too snappy to be used effectively; in trying to simply walk one way or the other or perform a move aside from the special, you'll usually accidentally tap it and dash, either into an opponent's fist or off into oblivion, or perform your special when there's no opponent around to notice it.
Maybe i'm flawed in my reasoning. I am, after all, comparing this to how quickly i became accustomed to the controls in the Street Fighter series. Within 30 minutes, i had those controls down, regardless of which SF it was. But with SSBM, i've messed around in Training mode with a couple characters, played through Classic mode with 3 different characters, beat the Target Smash games for nearly all characters, smacked that punching bag a few times and passed half of the Events and still the gameplay infuriates me.
Graphics & Sound - well done, obviously displaying the adequate budget & time spent into making the game. Gameplay is fluid, sounds are fitting to the characters & their moves, and stages are lush & appropriately designed (example: Yoshi's stage is colorful & reminiscent of an Easter egg while Samus' stage is dark & broody, like the Metroid series).
Many of the famous Nintendo universe characters are well-represented, from Mario to Link to Kirby, as well as some obscure characters (those snow bros & the little psychic kid??) and specially licenced characters (Pokemon - gotta catch em all!). Lots of extras in the game, like mini-games (smack the punching bag!) and special events (like Mario fighting Bowser in an epic duel that has spanned decades or having to defeat Pikachu using only pokeballs & the pokemon within). Also lots of unlockables, like more characters and trophies... so so many trophies...
Multiplayer is probably much more fun, since it involves other people and most likely a party of one form or another, but the control downfalls would still get on my nerves.
Maybe if i grew up playing SSB on N64 i'd have a better understanding & appreciation of SSBM, but as of now i've only played the N64 classic once and have yet to get used to the controls & quirks of SSB:Melee. Or maybe my expectations are too high.