In addition to the Subspace Emissary, you still have Classic Mode which has you picking a character and then fighting through a series of progressively more challenging battles until you finally reach the final showdown with Master Hand. If that isn't enough for your single playing needs, you also have a total of 62 new Event Challenges (41 single player, 21 cooperative), new "Break the Targets" courses, an improved version of the Home Run Challenge, and improved Multi-Man Brawl modes, all of which, like the Subspace Emissary mode, can be played cooperatively.

And for the perfectionist who believes that games aren't truly beaten until 100% of everything is found, there are a plethora of unlockable stages, songs, trophies, stickers, and even trial versions of classic games that made the characters in the actual roster the stars that they are today. Even if you completely ignored the multiplayer aspect of the game, Super Smash Brothers Brawl is still a game that would keep you busy for a very, very long time. Why you would want to ignore the multiplayer aspect though is another and very perplexing story.
There, now that we got all of the single player stuff out of the way, we can finally get to the real meat of this review. The actual brawling.
Let's talk about the roster first. There are 35 characters this time around, and that's not even counting Sheik, Zero Suit Samus, Charizard, Ivysaur, and Squirtle as separate characters, so in reality you're actually looking at a total of about 40 unique characters. Pretty much everyone from Melee has been brought back for Brawl with the exception of Dr. Mario, Mewtwo, Roy, Pichu, and Young Link.
Honestly though, with the exception of Dr. Mario, none of these characters should be missed due to the fact that each one besides Pichu, who was just all around awful, has been replaced by a similar, but much better character. Ike for example, plays like a slower, but even more powerful version of Roy with a much better moveset.

On the other hand, nearly every aspect about Pikachu has been improved, Kirby now has a real dashing attack and not that crappy fireball thing, Zelda can now hold in her own in a fight without having to switch to Sheik, and Bowser has a kick ass new special move that he can use as a suicide attack to bring his opponent down with him.
There are still characters that are clearly better than others, but from the looks of things right now, the gaps between the great characters and the not so great characters is a lot smaller than it was in Melee.