There's nothing quite like the first time you have sex with a new person. There's an element of permission-seeking, of discovery, of tension that will never be there again.
Neither of you knows exactly how far the other is going to go. Oh, it may be damn obvious where you're headed and you may have even said it aloud, but there's still a sense that every touch is a risk. I touched his thigh, and he liked it; dare I go up an inch? Of course I dare, and of course he likes it--now another inch. If I ever fuck him again, I'll know I can go for the goods, and even if I draw it out it won't be the same.
Another silly fear: oh god what if he doesn't have a penis? Or if it's really tiny or weird or something. Of course this is ridiculous, of course he would warn me if he was very physically different, but it's still such a strange sense of relief and joy to clasp your hands around something really nice in his jeans. I love the feeling of a man's cock in his pants, being able to trace the outline but not quite hold it, to make him feel it but not quite stroke him.
Not just the cock. Every inch of his body is a discovery. Where he has hair, where he has muscles, where he's soft and where he's rough are all new and wonderful. Are his nipples sensitive? How does his skin respond here, and here, and here... ah. Finding the right spots to draw those little gasps out of him is a journey that will never be the same again.
First-time foreplay is longer and more amazing than any other kind, which makes it a bit of a letdown that first-time intercourse usually sucks. No two bodies fit together in quite the same way, and an "ow," "oops," or "sorry" is nearly guaranteed. But when it works, even fleetingly, it's just that much more rewarding.
I like coming, but that's nothing new; I know what it's like when I come, fireworks, screaming, clutching, quivering, whole skin on fire, post-ictal phase, yadda yadda. His orgasm is all new to me. Some men scream and moan; some close up their face and body and just grunt; some look almost unmoved; some throw themselves completely into the motion and just rock with me. However he comes, it's animal and beautiful.
Fucking a new guy is like listening to a new band; the instruments are all the same and they may be played much the same ways, but the sound is fresh. Even if it's not good, the sheer newness of it is something the best band in the world can't replace. Can't listen to a different band every night, of course; most of them suck and it's good to be a steady fan when you find someone really talented. But there's just nothing like new.