my most masturbated to porn star is easily Jasmine Byrne, but when i was younger and first started to get into porn in a big way it was people like Jenna Haze, Taylor Rain, Gauge, Aurora Snow, Brianna Banks, but from first seeing Jasmine in action I was hooked and like MrStiffy said I keep on going back and watching her scenes from time to time.
In the non porn world i would say Jenifer Lopez would be the number one, had a huge crush on her when i was 17 and she was involved in a lot of my fantasies.