I've been playing this game with my brother ever since it came out. We've managed to unlock all the characters and are in love with the Subspace Emissary mode.
My better characters from the last two games are still some of my best ones, mainly Yoshi, DK, Ice Climbers, Captain Falcon (
still the epitome of manliness!
), Bowser, and Ganondorf. The newcomers that have joined my main list are Dedede, Ike, and Snake.