I say so because
Hal Jordan is a goldmine. After his return, GL has thrived in the franchise.
Hal Jordan has been in the lead role in all the animated movies since his return which includes
Justice League New Frontier
Green Lantern First Flight
Justice League Crisis on Two Earth
Green Lantern Emerald Knights
Justice League Doom
Green Lantern The Animated Series
Hal's return have revived the line so much that he led into 4 events in DCU, 2 of which are line wide events (Blackest Night and Brightest Day) and Blackest Night stayed on the new york best sellers for months.
He also starred in a live action movie, which although underperformed, but still made 200 million which means it had reached to a pretty wide audience.
There is no way in hell WB would substitute Hal with any of the other Green Lanterns. Because he has had the most mainstream appearances and the franchise thrived after his return.
After the formation of DC entertainment, Diane Nelson pulled back all the other movie projects to really concentrate on hitting the mark. They did well with new 52 and have tried to build up the Justice League brand by making Batman Lego DC Superheroes,
Injustice which would likely feature Hal as GL.
Also all the Justice league animated movies appearance of Hal Jordan has been around to build up his presence in the mainstream audience's mind.
So I believe he would be the best candidate for the Justice League movie since he has already the largest fan base.
Additionally: If the Justice League is to include Green Lantern in a DC cinematic universe, then its important that Carol Ferris plays a big part since she would be the leader of Star Saphire and Sinestro is Hal's arch nemesis. I just don't see how any other earth GL could take the lead role of GL if Carol Ferris is involve unless they stray so much away from the comics. All these characters, Abin Sur, Sinestro, Carol Ferris are so much attached to Hal, that if they were to remove Hal Jordan and replace another GL with Hal it would pretty much be replacing him in name but have all of Hal Jordan's stories. Similar to what Superman the animated series did when they included Kyle Rayner as the GL but have Abin Sur give him the ring.