I didn't think it could get better than the first one. I was wrong.
First, with the story. The Patapon tribe is sailing to a new island in search of Earthend, when suddenly they meet a giant seas monster which wipes out the boat and (supposedly) killing all of them except for Hatapon and three Yaripons. Thanks to not reading any spoilers whatsoever, I actually found all of the story nice and exciting with some plot twists (like Gong becoming an actually helper).
The graphics are still the same as the first game, meaning that they are beautiful, detailed backgrounds and characters.
The gameplay still remains the same also, but new songs are added. Many critics criticized the game because of its similarities to the first one in gameplay, but why? I'm not sure what they were expecting, but I was expecting the same gameplay in a new adventure.
Gamespot didn't like the evolution tree. I do. There are many more rarepons to unlock now, and you can level them up too. Also, you don't have to sacrifice a current patapon to upgrade now. And if you got a strong helm, you can always go back to a normal patapon and try it on then.
The length of this game is awesome. As it says above, I've only played 20 to 40 hours right now, and I've still got many more minigames, levels and patapon classes to unlock.
And finally, the difficulty. It's what you'd expect from a Patapon game. Really hard boss fights and war levels. Don't worry though, you can always change the difficulty.
What adds on more to the game is local multiplayer. You and your friend can play any levels you got an egg from, even if your friend doesn't have Patapon 2.
All this adds up to a very worthy sequel. The critics keep saying "It's just an expansion pack of the first one!" but after all, that's what I've always wanted.