Again, sorry for the 12 :( I did these not 2 days ago! Plus it's been two months of 13 :D
I think they're pretty good. My only criticism on the Superman drawing is that the head looks squished vertically. What always helps me avoid this is to make sure I lay out where the features will go before I start drawing a face.
First drawing: Rough lines, but they work pretty well.
Superman drawing: I like that there arent too many lines for shading and stuff like that. Also, the proportions of the body look pretty good.