While Deadpool's graphics aren't going to blow you away, it never feels lacking. The game doesn't try to go for ultra-realistic visuals or even attempt to put you into the comic book world with fancy shaders or overlays. That being said, Deadpool still looks good with tons of details in the levels and the character models. While each type of enemy grunt looks like another of its class, the named characters definitely look the part.
Of course, Deadpool himself is the star of the game and his model is filled with detail so whether you are slashing your swords, swinging your hammers or shooting a small arsenal of weapons, the red and black suit looks good. As a bit of polish to his particular model, as Deadpool takes damage, his suit will get torn up to reveal his scarred flesh. Granted, somehow his healing factor also heals his suit, but this is not just a game featuring Deadpool, but one that he helped develop so he isn't going to stay ugly looking for very long.
As for the other Marvel characters, guest appearances include everyone from X-Men like Psylocke, Domino and Wolverine to little heard of villains like Blockbuster, Vertigo and Arclight. Even in these fairly minor roles, the characters look the part. More screen-time is given to characters like Cable, Rogue, Mr. Sinister and Deadpool's love interest, Death, so you can expect even more care to sell the looks of these characters.
As for the game's audio aspects, Deadpool and his two additional voices are played by Nolan North and quite frankly, he sells it well. While it might have been nice to hear Ryan Reynolds reprise his role from the film, I'm not actually sure he could pull off the effect. I can't really recall him playing a truly insane character before; but I guess we will find out when the Deadpool film comes out.
The game's music is loud and powerful when the action is high, but does a good job of quieting down and getting out of the way when the dust settles and you simply have to get Deadpool to the next killing field.