Just beaten Prototype 2. Felt more mainstream compared to the first both in good and bad ways. It's more polished but has less freedom to customize the main character, controls and movesets are similar but there's some tweak, you need no grind but it ends in 8/9 hours (client says 8, web says 9, in the first one I've spent a lot more time) even doing a bit of side missions, no particular threats from enemies and last boss is much easier.
If you liked the first one, the second is at least interesting to play.
Took me 17 hours to beat Prototype 2.
I played both for the first time, back-to-back recently, started with Prototype 2 and then played the first game. Prototype 1's power/level-up system is terrible. It's just a menu, there's no context, connection, no design introducing and tying these mechanics to gameplay it's just lazy. It's just there. You earn points and then just select some shit from a menu. It's so arbitrary and detached.
I loved in P2 how if a boss had a power, you would kill that boss and absorb its power Mega Man-style. The power would then be tied into the design of that or the following mission, you would be provided context for how to use a power, like why it's useful for defeating certain enemies. Power-ups for your abilities were even tied into the gameplay, you see a tank enemy in the open world with a genetic marker icon, you drop whatever you're doing, kill, fight and absorb that enemy to gain a power-up.
The stories in both are terrible and the protagonists are both unlikable douchebags but I found I enjoyed the gameplay more in the second game.