I can't say much more than that. Its bland and watered down. They spent too much time introducing the character considering that they barely delivered a character (and had to graft Kyle's personality onto his just to tell the story they wanted to tell.)
The problem is this. They couldn't introduce the Green Lantern Corps and Hal Jordan's human life in the same movie. They tried to split the difference and got nothing as a result.
You may think the answer is to spend more time on those human characters but that borders on Bait And Switch
. We're here to see the movie about the space cop with the magic ring.
What you should do in the first movie is give us what we came here to see, the space cops and the magic rings. Give us grand glorious space battles, introduce us to this fantastic setting. While we're here for the spectacle, lay out some intriguing hooks about Hal Jordan. Our butts are in the seats enjoying the light show and we're starting to get to know the character through his actions.
THEN next movie you go personal. You develop Hal more. You develop Sinestro more. They were friends in the first movie. Now you make it personal and make them turn on each other. NOW you can show us his human life.