I didn't think Green Lantern was that bad.
Sure it could have used a little less Tim Robbins, but that's true for every movie he's been in.
I enjoyed it a lot, and Warners made their money on it - but not nearly enough to make it a success justifying a sequel. One can see in retrospect that Green Lantern
is a problematic movie concept without a lot of retooling to the story, but there's no reason the character can't work well in Justice League.