Ratchet and Clank is one of my favorite Playstation series of all time. I have played almost all of them. My top 3 are the original 3 for the PS2 which I have the collection for. Going Commando is my favorite, I love everything about it. Ratchet and Clank is my second favorite, even though it has the best story in my opinion. Up Your Arsenal is my 3rd favorite. I just didn't like it as much as the other two.
My favorite character is Ratchet, although I do like Clank, Qwark and the Plumber ("Hey look, plumber's crack") a lot. Favorite villain would have to be Chairmen Drek (Doctor Nefarious is cool as a villain, but his voice is soooo annoying) and my favorite planet would be Kerwan (Metropolis) with Rilgar (Blackwater City) coming close.
Also, is it just me, or does nobody play Ratchet and Clank: Up Your Arsenal multiplayer for the PS3? If there were people on it, I would play it.