This game is pretty much "more of the same." Pretty much follows the original, but does feature some new things like the ability to change between Humanoid, Blob, and Spider form. Other differences include the complete removal of Lives, and the ability to start off with one of three weapons. Abilities are mainly removed, instead you get addons to your weapons. Regardless I mainly played it for the story, and god, the ending dropped a huge bombshell.
It's a shame there can't ever be a third installment.(Play the game to the end and you'll understand why.)