I've wondered that myself. The closest one is probably the one that came during the DC Superheroes line (Prior to DCUC), but even that one wasn't perfect. He's a little on the short side, eyes are constantly looking up, and has a little bit of a hip problem. I've heard the "mullet" version in Wave 6 is pretty decent, but it still isn't the "real" Superman. They could really stand to go all-out with a true version of the boy scout - just looking at the recently released Flash, as well as Green Lantern, Aquaman, and Wonder Woman - those are all pretty perfect for each character (as well as a handful of Batman figures) - so Supes could use an upgrade.
On a side note, there hasn't been a lot of DCUC around here lately. WM still doesn't carry the line locally, and Target has had a Firestorm and Cyborg on the pegs for awhile. TRU has had some Wave 7 (actually still does), so that has been the place to be. I've been surprised to actually see this line "sit" for a bit, but TRU has had a couple of Kid Flashes, Barda (including the variant), and Captain Colds on the pegs for a couple weeks now. Flash seems to sell out right away, but otherwise it seems to be sitting - which is surprising to me.