It's really hard to describe what a feeling "feels" like to someone else that can't experience it. It's be like telling someone who was born blind what something else looks like, no offense. If I had to try to explain what my foreskin "feels" like, it would go something like this:
The outside of it feels just like regular loose skin (on any other part of your body). Not too sensitive, very loose and easily manipulated. But underneath (the inner foreskin), it's much more sensitive to touch because it's more of an inner mucosa membrane (similar to the inside of your lips or underneath your eyelid). Pulling it back always feels good (whether you have an erection or not) because it folds back over the corona (ridge of the head) everytime. Of course when you have an erection and do it over and over again, it obviously feels much more pleasurable! The most sensitive part on the penis is the frenulum (small "V" shaped flap of skin underneath the head which connects to the foreskin). For some reason that is the "sweet spot". Some circumcised guys still have the frenulum, or part of it, so you may or may not have it. That's about the best way I can think to describe it.