It's actually quite an interesting question, and one that made me think quite a bit, oddly enough.
I don't masturbate as frequently as the average twenty year old, but when I do (as odd as this may sound), I don't just do a quick rub and tug for release, I almost... I don't even want to say it but, 'make love' to myself. Touching, teasing, stroking... slowly bringing myself to orgasm, enjoying the feelings the touch of my hands provides for my body just as much as I enjoy the feelings that touching my body provides for my hands. Sometimes, if it's after a shower and I'm getting particularly into it, I'll even sit upright, bend forward and suck myself (this post is starting to feel like it should go in the 'confessions' thread

).
In that sense, I feel like masturbation
is a form of sex with myself. However, if faced with myself as a separate entity, I'm not entirely sure as to whether I would go through with it or not, but I'm leaning towards no. To me, sex with someone else is an expression of love (no, I'm not saving myself for my one and only prince charming

but some form of 'love' and 'affection' must be present), and I simply don't have those feelings toward myself (is anyone
really that narcissistic?

).
I'd rather share my body with somebody who is excited by it; excited by me. Somebody who is going to explore it with the zest of a person unwrapping a gift on Christmas morning, and someone who does it with a tender and intoxicating expression of love. Something that, for myself, I cannot provide.