MSG4 + Arena + Qwark + Some fun
The stealth is with Clank. theres no cover system, only way to get around is to patternize. You watch the movements of enemies and stealth take them out with a button combo. You can also hide in bushes and such.
Ratchet has arena based challenges like in the ps2/ps3 games. You get Bolts and silver bolts from this. These are couped with hard challenges and some comedy.
Qwark has these stupid fantasies, but its funny. such as saving space nuns and being a cowboy. No real challenge, only frustration.
The graphics are to date with PSP and the levels are well-made. There are also Insomniacs exotic weapons such as an ink pen which blinds nearby camera's and a tie-a-rang which can hit multiple enemies in one go.
There are skilkl-points which adds replay value. You can blast through this game in about 20 hours getting most skill points and doing most challenges. After that you probably won't want to play the game over.
The only bad thing I can say is that the levels, all of them, can get frustrating. The enemies will spot you magically, Ratchet's level's can get difficult as time progress's and Qwark's levels can get to a stage where you have the UMD 1cm away from being burnt in a blind rage.frusration.