I’m not sure how “fringe” he is, but generally Green Lantern is one of the mainstays of the Justice League. No matter the incarnation, he’ll always be a formidable hero in the DCU.
Maybe you think of him as “fringe” because he typically doesn’t get the press that Superman / Batman / Wonder Woman / Aquaman get. I mean, Aquaman gets better press, and he talks to fish, for God’s sake. Somebody needs to get GL’s publicist on line one.
Still, while he’s not one of the Big Three, he’s still a fairly formidable hero. I think a lot of the cult following stuff is based around a “Hal or Kyle” argument that’s been going on since the mid 1990s.
BTW, for the non-fans, long-time GL Hal Jordan was suddenly turned evil by writer Ron Marz (IMHO) for shock-value and to revitalize the franchise. Enter new GL Kyle Rayner. Ever since, fans of the original GL have clamored for a return to grace for their fallen hero, and fans of the new GL have argued that Kyle is a better replacement. Now, a new twist to the story – Hal is finally being resurrected, and Kyle…? No one seems to know what will become of him.