I stopped playing Brawl after a couple of months from its release. The time enough to finish it and play some free for all with my friends. Then I figured out that I was not having fun with that game, and returned to Melee.
Today, I still play both, Smash 3DS in single player, and Melee with friends.
When Smash 4 will be out on WiiU, I'm planning to play both, Melee and Smash Bros 4 with friends... the 2 games are different enough and yet fun to deserve being played both, alternate for the sake of variety.
Brawl does not exist to me, I was so disappointed by that game.