It always sort of bothers me when I see the difference in quality of masturbation between art and real life. Here, it looks like an utterly mind blowing experience, when in real life (while not a girl so it's not quite the same) I tend to find it far less awe-inspiring (and groan inducing).
I suppose it would be odd to say one prefers a picture where the target seems almost bored by the process, but at the same time, my suspension of disbelief nags at me.
In the world of hentai, even the most simple sexual act is a mind blowing experience. But it depends on how turned on you are most of the time. If you fap 4 times in a row, of course you'll arrive to the picture up there.
The arch-backed thing, however, can be achieved easily with a partner, since he / she won't know when you reach a climax.
I think it's a well-known fact that women simply have more intense, longer lasting orgasms than men do. That, and they're lucky enough to be able to do it multiple times in a row (while men go limp, us poor bastards!). On the down side, they menstruate, so...I can't honestly say I'd rather be a woman.
I don't know why I'm going to bother telling this to a bunch of anonymous interwebs people, but...personally, I can induce fairly intense orgasms by coordinating the following while fapping [TMI alert]:
Using the stop-and-go technique; being completely naked rather than just having my pants down; "sucking in" or applying pressure to the area between the stomach and pelvis; applying more pressure to the sides of the penis than the top and bottom; allowing my hips to "squirm" from side to side; trying to "hold it in" just as I'm starting to come...and that's about it. [end TMI alert]
About the whole moaning in ecstasy thing, it kind of depends on whether or not anyone's home. Although the possibility that someone could catch you makes masturbation (and sex) more exciting, we've all been kind of conditioned to be quiet anyway. But hell, if I find myself all alone in the house, I find that it intensifies things just a bit more to let myself vocalize a bit while fapping.