Prototype is like Crackdown meets The Darkness meets Hulk: UD
Prototype mashes the exploring elements of Crackdown, the dark creepiness and overall graphical feel of The Darkness, and the chaotic over the top battles of Hulk: Ultimate Destruction together into a nice mixture to create a wildly entertaining piece of software.
As much as I liked Infamous for how polished it was and had a good story, Prototype is better because the combat is more engaging with more options and the locomotion (movement) feels better.
Prototype is such a great pick up to play for 5 or 10 minutes or hours at a time with a nice save anytime system. The main story also supports this pick up and play system as there are 31 story missions and a 140 web of intrigue memories to find and consume to reveal the story. In addition to completing the story there are 50+ additional side missions and 250 total orbs to collect. Some of the achievements/trophies are for the hardcore plays: Like the Trail of Corpses one ups the Dead Rising and Left for Dead by requiring you to kill 53,596 infected enemies. There is a one for completing the game on any difficulty without dying, or the very hard achievement that requires you to complete all side missions with Radical medals (which is the medal above the gold medal).
I really really enjoyed Prototype, its the most fun I have hard this year so far and thats saying alot because we have had a great first half of a year so far with RE5, InFamous, and Red Faction already. Bottomline is that Protype has its faults like any other game but the gameplay and fun factor far out weighs the issues. I suggest a purchase as this is the type of new IP we as gamers always are screaming for thru the suffocating pile of WW2 and first person shooter games. New IP's like Prototype and InFamous need our support, I have done my part, its time for you to do yours and support these great games, they will provide you with some great experiences this summer.