This is tricky. If you were omnipotent, the success rate for solitaire would be very high, though there would still be games that you could not win due solely to the randomization of the deck. The problem is, there isn't exactly a skill to it- the order in which you choose the cards could be beneficial or detrimental depending on the rest of the deck. That being said, It also depends on which style you play. I've played quite a few games (actually, more than I'd like to admit,) and my success rate is a pretty steady 11%.