Highly entertaining and addicting game- I beat it within 2 weeks of purchase, although it is long.
Graphics: Nice cel-shading. The graphics are very stylized, you'll love em' or hate em'. I think they look pretty nice, for the Wii, but overall it is too dark. The graphics are too heavily shadowed, which gets kind of annoying. Very colorful, when you're out of the shadows. As gamespot said though, camera can be an issue (especially on one boss fight) and frame rate does get pretty crazy at some parts.
Gameplay: This is why this game is so great. The general button-mashing seems simple at first, and it is, but eventually it is very strategic, especially when fighting masses of enemies. My favorite thing about this is the wrestling moves, you swing the Wiimote and Nunchuck in the same (or different) directions to do "Lucha Libre" style moves. The real defining factor of this game for me is the boss fights. They are extremely epic and generally pretty fun (cept' for Holly Summers). This game is pretty easy on Mild (Medium), haven't tried it on bitter. Worst part is having to repeat side missions and assasinations. That is really annoying, and I can't beat those free-fight missions even with my character twinked out.
Story: This is a crazy story. Without spoiling too much, at the end, there are many twists thrown at you, especially if you get the "real ending" (I did). The characters are engaging and funny (see Destroyman). They didn't go overboard with the story, but they did make it way better than expected in an action title (I thought Zack and Wiki would have a good storyline, it sucked).
All I can say is, get this game if your parents would let you. It is rated M, super gory and violent, especially when you kill bosses. Also, tons of swearing (F*** you, ya little prick). Don't worry about the sexual themes, unless you haven't really been exposed to that stuff before. He does collect pornography, although it is a minimal (at best) part of the game, just when a video rental store asks you for movies back (69 positions part 2, for instance). GET IT!