Fun is the bottom line here, and even with the online portion not being entirely up to snuff upon release, Super Smash Bros. Brawl is an incredibly fun game, when played solo or with others. It's hard to find a game out there for the Wii that provides more value for the money, or has more to see and do.
The huge roster of well done, interesting characters combined with the wackiness of the in game items and the interactivity and challenges of the various stages packs the game full of memorable moments regardless of which portion of the game you decide to spend time with. It may sound silly to say that a video game can make you feel like a kid again, but it brings you back to the frantic fun of the playground, and to the "who-would-beat-who" discussions of your youth. A-/A+