I was wowed more by Melee than I am with Brawl now. I suppose the Smash dojo spoiled a lot, but at the same time, I feel that Melee was a much larger jump in terms of well, practically everything.
As you probably know by now, Subspace Emissary just didn't do it for me. Too many reasons why. And too many reasons why it should have been scrapped for more of what series fans really wanted.
Ultimately, they should have focused strictly on multiplayer, like Miyamoto wanted. Comparatively, Melee did much more in terms of refining the gameplay without disrupting the core. For example, the addition of charged smash attacks and an improved defense system among other things made the game feel completely different. I, personally, felt that it was nothing like the original. I had to essentially learn a new game and I didn't mind because Melee did all the new things well.
Brawl is very, very close to Melee in almost every way. The Smash Ball and Assist Trophies are interesting additions, but don't change the gameplay as much as the charged smash attacks did or 4 directional throws in Melee did.
Over the years, I've heard and even came up with a couple interesting gameplay additions I felt could have spiced things up in a new Smash Bros. I could give examples but I don't want to derail Mashiro's topic (if he gives the okay, I'll go over a few of them). The ideas are there, fans have talked about them for years and most of them, I'd say, still fit into the simple yet deep gameplay that Smash Bros. provides. It's these kinds of gameplay additions and refinements that's really missing from Brawl to set it apart from Melee.
As a fan of innovation and new gameplay mechanics that really change the fundamentals of a game, I'd say Melee was more fun than Brawl. At the same time, Brawl, so far, has remedied Melee's one glaring flaw: its unbalanced gameplay which, in the long run, may give it the edge.