If they needed to show Green Lantern overcoming his fear, then they should have used Kyle Rayner. Hal Jordan has always been pretty much fearless (to the point of being stupid sometimes.) But again, this brings me back to another problem I've always had with the character, and that is that Hal is the least interesting of the main lanterns. Green Lantern is not all that cool. Now, the Green Lantern Corps, that is AWESOME! That's what the movie should have been about.
Well I think they kind of HAD to use Hal, seeing as he is the most iconic and recognizable of the Green Lanterns.
And I thought casting Reynolds was a great way to actually make him seem somewhat cool and interesting for once. It's just a shame the movie had to go overboard with the angst and turn him into as big a pussy as it did.