It's sad that games rely on multiplayer/online play to even be fun. While Brawl and Mario Kart Wii were fun at first playing solo, they're just about impossible to play alone now. I'm an advocate of games that can be equally fun playing either solo or with others. For instance, the new Guild Wars game (Guild Wars 2) is being built so that people can play alone if they want and have just as much fun as they would if playing with others. I was a player of Guild Wars, but when everything was built around level-grinding and PvP and all players shifted to that mean of play, I quit because every ounce of fun was drained. Repetition didn't help either.I'll have an urge to play the game for like, 3 days, but I don't get around to it for...well, about 3 days. Then I finally pick it up, am psyched to play, play one match, play another match, turn off the Wii and return to playing Pokemon, posting here, or editing Pokemon.
When it comes down to it, it is just a party game. Which is why the only time I play for very long is when hanging out with a friend. Spear Pillar is very fun to play with a friend because it's just so freakin' random. As long as Creselia's not there. So is Norfair, because I baffle my friends (somehow) by just jumping over the lava rather than going in the capsule while they try (and fail) to get into it. Plus it's a Metroid stage, making it awesome. (Despite the fact that the Theme of Super Metroid was wrongly called the Theme of Samus.)
...But I'm getting off-topic. Point is, Brawl is pretty much nothing but a party game, and gets boring in any other context.
Now, the beauty of single-player games is dwindling unfortunately. At least we still have Zelda and Metroid, because those are prime (hawhaw Metroid Prime) examples of great single-player experiences and are built for playing alone only. Why build a game as a "party game" only, when if you could extend the single player experience to be equally as fun, your game would sell even better?