Thank you! Took the words right out of my mouth. Brawl should have been 3.5x as much better than SSBM than SSBM was better than 64! (Okay, that's pretty impossible, but still; they could have done a lot more, or at least kept all the characters from Melee in it and not nerfed a lot of the good characters.)
Like what? Melee was such a dramatic upgrade that nobody could seriously expect Brawl to be just as big an upgrade, unless they expected Brawl to be a completely different game - which would have upset all of the fans that loved Melee so much. You see, the reason why Melee was so highly praised was that it was simply better than the original - the control was far smoother, the game played faster, there was many more attack and defense options, etc - basically, it was nothing like the original except in basic format. And for the most part, people loved the change.
Now, if the developers applied the same logic to Brawl, we would probably end up with a game that played nothing like the previous two Smash Brothers - and also probably wouldn't be an actual improvement. Some people might like it, but for the most part people would be angry that they didn't stick close to the highly sucessful Melee engine. You just can't improve much on something that's already near perfect, and that's why Brawl is so similar to Melee.
But, in the process, we also got a huge mass of unlockable content unlike anything else we've ever seen in a fighting game, many wanted characters, removal of characters that were usless, many amazing new stages, and far more options than ever before - just to name a few things. Sure, Quantity doesn't always equal Quality, but since the core game of Brawl is just a small upgrade to an already awesome game, I think a lot of us can say that it DOES apply here.