Great game with much to unlock, but single player wears off quickly. It falls a bit short to it's hype.
Enemy A.I. at the harder levels seemed to improve from Melee, which is a good thing and offers more challenge. Graphics hasn't improved greatly over Melee, but Brawl is definitely more colorful and feels more fleshed out. There's new characters and even bigger roster of fighters. Unfortunately, some characters feel like "clones" of others. Other characters feel out of place like they don't really belong, i.e. Olimar and Wario. Characters like Roy, Mewtwo and Young Link were removed, which in my opinion was extremely foolish.
One gripe I have is the controls. Personally, the Wiimote wasn't designed for fighting games, making the Classic controller or Gamecube controller necessary to feel in control.
The biggest letdown was the online. I use a Nintendo WiFi adapter to get online with my Wii. Yet almost every match I've played online had lag issues and sometimes will disconnect. Hopefully, this will be remedied in an update soon.
Brawl is at it's most fun when played with others. 4-players can free-for-all or team up. Item appearance can be customized like previous games and the new Final Smash attacks and assist trophies add more variety of attacks, even though it is overpowered.
The one thing I will give Brawl a perfect 10 is the soundtrack. From classic Mario themes to MGS music. The number of composers involved is nothing short of amazing. Brawl delivers fully on music and sound.
Overall, Brawl is really good game, but it was a victim to it's own hype. Brawl was designed with multiplayer in mind, hence why it's story mode, Subspace Emissary was a bit lacking, even though it was fairly enjoyable. Online needs some tuning, etc.
Super Smash Bros. Brawl was one of the reasons I got a Wii, I'm still glad I did, even though Brawl is basically Melee 2, with more content and online. I have no regrets about this purchase.