Innovation is average, but Fun factor is through the roof
I am going to review this on how is the playing experience while you are playing it, the game flows really nicely, actually it is pretty much like the first game. There is not much frustration where you die over and over and have to restart at a far checkpoint somewhere far behind.
The difficulty is just challenging enough that make you feel like you are beating them and have fun doing it, and yet, not so hard that that make you lost interest in doing them. I didn't care for collecting all the little pieces of achievement in game, all I wanted was to play a fun, action filled game and I got exactly what I wished for.
However don't expect any changes and new experiences from this game, it pretty much uses the same formula from the last game and many game in it is genre, that that does not mean you won't have fun playing it.