No I prefer to play by myself.

Yes, with some exceptions. I can't imagine playing Corpse Party would be as fun as watching Cry play Corpse Party.

Games like The Last of Us, Heavy Rain or Uncharted I have no problem in watching someone else play it. If the game requires skill and heavy interaction I get bored pretty easily watching someone else play it! Games like Zelda, Mario, etc. I really need to feel the controller in my hands for those kind of games.

The only time I watch people play games is when alternating turns with someone. I don't understand let's plays or spoiler blogs at all. Even worse, is people who "watch" someone play a game and then feel they are now qualified to review it. WTF is that?

I find no enjoyment in watching other people play video games. I'd much rather play them myself.
Also, I cannot stand half of the LPers out there. They're either very fake, make terrible puns or sound bored to death. Only people I find enjoyable are Cr1TiKaL and MWN.

Depends on what mood I'm in, sometimes I like watching, sometimes I need to get in the action!

Only if it looks fun (but not frustrating) to play and is widely considered good

I try to play everything. The only time I watch a game is if I'm on the fence or if it's some SNES or NES game that I used to want and never played or something.

I watch more games than I play. If a game can be entertaining to just watch, it's not worth owning in my opinion.

The only game where I find watching is as good as playing is FIFA.