What's better than playing as Spider-Man? How bout playing as Venom!
Partway through the game the story splits off and you can choose to continue as Spidey or as most of you will probably do, you get to play as Venom. Venom is noticeably slower than Spider-Man but makes up for this with improved strength. Venom's moves essentially mimic Spider-Man's only using his symbiote instead of webbing. The rogue gallery is a lesser-known bunch straight out of the comic storyline featuring Shriek, Carrion, Doppleganger, Demogoblin, and the title villain Carnage. The villains aren't terribly tough individually but keep teaming up in the later levels which makes things considerably more difficult.
The only thing this game really lacks is the ability to play two-player co-op with Spider-Man AND Venom. It is only a single-player game but in it's own right is still awesome. The game is very long for a side-scroller and features no game saves. This is another game that's pretty tough to beat but can be done. Definitely worth picking up when you get bored.