I love all three gentlemen's work, but when I think about their 'iconic' moments, I never really consider Hellblazer. It's not that their work on HB wasn't excellent, but it never associates in my head with a definitive vision of John. With Corben, I immediately jump to Den. With McKean, it's his Sandman covers. Bisley, it's Slaine. (I'd also throw Steve Dillon in here-- I think about Preacher or Judge Dredd.)
Even though Sean Phillips has gone on to do work that is better on a quality level since HB, I still think of his HB work first.
It's strange how a particular artist's depiction of a particular character can imprint so strongly on your conception of them to the extent that it almost becomes difficult to consider other artist's depictions. And I consider myself a pretty open-minded guy to different artistic styles.