Hmm. Well firstly I hate the ever loving hell out of Empire State of Mind because that song has been over played to hell. Seriously, if you can find an ad for something even remotely New York related that doesn't use that song, I will go buy a hat and eat it.
As for California Girls (I refuse to use the retarded spelling), it just came across as terribly cheesy to me. Like, absurdly cheesy. I had three thoughts while watching the video: 1.) Well this is pretty damn corny... 2.) I remember when Snoop had street cred... and 3.) Holy boobage Batman!
So in my mind, I'm going to say that both are pretty mediocre songs at best, with ESoM probably being the better song, but California Girls wins out because I haven't had to hear it so much that I've developed a Pavlovian Response of diving for a mute button when it comes on.
EDIT: Seriously, this guy used to be straight gangsta