I've been playing Resistance 2 for a while, it's probably the best shooter on the system. Strongly recommended.
Valkyria Chronicles I would buy if I could FIND IT anywhere, which I can't. From the demo, it looks awesome, though, so get that.
Fallout 3 does not look exciting to me. I hear the PS3 version has bugs and frame rate drops, though. At least it's been patched with trophies. I would say avoid unless the idea of the game really appeals to you and you have faith in Bethesda's ability to fix glaring problems.
So I say R2 and VC.