Here's a description of the clip shown at last weekend's convention.
A clip of Superman Lives played at Comic-Con.
It's described on Bluetights.net as follows: "The footage starts out with a montage of Smallville that's absolutely beautiful. Then we get some shots of young Clark busting through the barn roof, and examining his baby ship. We then jump to Martha Kent and Ben Hubbard in the house staring out the window in horror, apparently looking at Clark's crashing ship. Then there's the shots of Martha approaching the ship. We cut to a shot Singer described in the Kent Farm blog about Brandon sitting up into the frame in front of the window. We then cut to Metropolis with a lot of shots that look into the relationships between the characters. Superman's return has prompted Perry to tell Lois to write an article about Superman, though she's very opposed to it. Richard White, her current boyfriend also is shown being a bit jealous of Lois having Superman back in her life. We got several shots of Superman and Superman with Lois, and they look absolutely FANTASTIC together. One great quote from Brandon in the clip was 'That place was a graveyard. I'm the only one left.' One presumes he was talking about Krypton, but we shall all see. Near the end we got some very cool, yet brief shots of Spacey as Luthor holding a Kryptonian crystal in his hand. The big finale was an animated live shot of the storyboard picture that showed Superman hovering over the clouds, but with the added bonus of him streaking down toward the earth, creating a sonic boom on the way. It was amazing."