In a recent interview with MTV Splash Page, "Green Lantern" co-writer Marc Guggenheim offered the following explanation as to why the film's Superman cameo was ultimately cut:
"Without trying very hard, you could probably find the leaked script on the internet. The Superman cameo is in the leaked script. It survived several drafts. Ultimately, it was cut for budgetary reasons. We took it out in one of our later drafts. After my interview with you, of course. The Clark Kent cameo is still near and dear to my heart. I really wanted it to be in the movie. You never know — it can still happen. If Tom Welling has a free hour or two, you never know."
Check out the complete interview at http://splashpage.mtv.com.
Oh well, poor Supes. Here's the GL Trailer again incase you missed it: