35 characters, 41 arenas, over 300 different music, more than 500 trophies, more than 700 labels and a good thirty different modes: Nintendo has seen big. One might say that doing so in excess impinge on the quality of the game, but it is not. Whether alone or (especially!) With friends, you will not get bored. Super Smash Bros. Brawl is undoubtedly one of the most successful games on the Wii, and even this generation of consoles.
NB: I did not test the online mode and therefore can not comment on it.