Ok i'm not expecting you to give a % score of "turn-on-ability", but if you can please try to say of the extra umpf you get from knowing your lovers eyes are seeing you so intimately.
From things like letting him/her see up your skirt to see your panties, and their eyes feasting on your breasts, at your cleavage or as your bra comes off. To having them knelt between your open legs, you or them opening your pussy lips and knowing they can see all your pink juice covered entrance and/or internal walls. Does that make your clit tingle and you juices flow even more knowing they are looking ?. Oh, and lets not forget their eyes looking up at you as their mouth and tongue goes to work around and inside.
It's a huge turn-on seeing the effect I have on guys (and girls!) when they see me naked! One of the reasons that cowgirl is my favorite position is because they can see (and play with) my tits. The very best reaction that gets me off, is when a guy is about to enter me for the first time and I can literally hear his heartbeat racing 90 miles an hour.
It is a while since I stripped for a guy and watched him watch me, but I have done it often enough and always got the same result - a bone hard cock to admire and make use of myself. I was usually the one who got him naked first.
Yes I did appreciate the eyes and comments that followed my removal of each piece of clothing particularly my bra - second last and my pants - finally.
Then to feel his warm body against mine as we kissed determined who got to get the forbidden apple first. One had to make the move and I never cared who went first but I always ensured he enjoyed an oral experience to slow him down for the main event.
That way I got to enjoy the experience we had together and reach the same conclusion he did. Like Bethany I found that feeling him explore my cave of pleasure as he prepared to enter me and then share the sensation together soon had the drums beating a similar rhythm.
As for another woman, that is a completely different and even more erotic sensation. We always strip each other together piece by piece as we embrace before those magic moments begin.. THAT is living.