It's a type of game you really don't see much anymore. Has a lot of fast paced action and replay value, controls are really solid, multiplayer is really fun, great atmosphere and music. Has a challenge to it that makes you want to overcome it and keep playing, and gives you a nice sense of accomplishment because of it that many games today just don't give you (which is why the cop out achievement/trophy system exists on the HD consoles, to try and manufacture a cheap sense of accomplishment that the game cannot otherwise give).
Has a lot of things going for it really. But overall it's just a lot of fun to play.. That's all ya need really, there's not much else to it really.. 2D platformers are the best genre out there IMO, and this is just 2D platforming at its finest, coming out at a time when the genre was near dead. That's pretty impressive.
Plus, it is the successor of a majorly awesome series, so it has a huge nostalgia factor for people.
