I've finished half of the main story of Super Smash Brothers Brawl, The Subspace Emissary. There were several very cool elements, including a section where you play Zero Suit Samus through a fight verses two dark bounty hunters in an effort to reclaim her lost suit. A great cinematic sequence of a vengeful suited Samus followed, accompanied by Pikachu, tearing up a legion of R.O.B.s.
There are some of the platforming elements of the story I could really do without. The side-scrolling "push" sequences where the levels autoscroll just about kill me. There are some really great parts, where you control characters at your leisure, specifically anything involving Donkey Kong Country-style blast barrels. All told though, the single player adventure is lots of fun.
I've managed to unlock several more characters for Brawl play, including Lucario, Snake, suited Samus, and Falco.
Will try to get some screens up later.