Resistance 2, it will give you good value for your money

Resistance 2. Has more bang for your buck. Co-op, multiplayer and trophies. You don't really have to play the first one to understand the story. Just read the summary from Wikipedia or something.

MGS4 will only last you six hours once you skip all the cutscenes. The online is a joke ATM. The story and dialouge is awful, and this is coming from someone who loves the other MGS games. The gameplay is great, but once you play it again, you'll feel bored with it.

My Littlez Ponyz 3

That will do.

Oh you mean game for PS3 and not for Wii?
Well unfortunately most of the games on PS3 are crappy/scalled back versions of the X360 versions, so I'd try some great exclusives like Little Big Planet, Valkryia Chronicles or MGS4. These are great games.

For multi platform games choose the X360 version instead, especially if the game uses UT3 engine which still not working well on PS3 . Shame.

Easily get Metal Gear Solid 4: Guns of the Patriots. Its a game full of win. If you must have a FPS then get Resistance 2. Because it has a 8-player co-op if I'm not mistaken, a nice campaign and a awesome multiplayer mode that holds up to 60-players if I'm not mistaken again.

But if you want a single player experience. I would go with MGS4.

Valkirya Chronicles. But if i can't recomended you a 5th opcion, i choose in this order of priority
MGS4
Resistance 2
Motorstorm 2
SC4