Friedl should be off the list - writing a vaguely competent "user" focused book that butchers the theory (in a way that's had long-running consequences for people's understanding of what an NFA actually is) doesn't put you among the regex greats. Much as I don't agree with many of his approaches to things - most, even - Russ Cox is a far better popularizer of solid regular expression implementation technique and Friedl should be replaced by Cox.

VM Glushkov should be on the list. His NFA formulation both predates Thompson's and has significant advantages for efficient implementation.