variable names are almost certainly a lost cause, but IDA pro is pretty good at recovering control flow, which could be turned into C constructs (didn't Dijkstra prove something about expressing any control flow using structured programming constructs?). You'd probably need a bunch of heuristics to tell the difference between a while loop and a for loop. More ambitious would be trying to un-inline functions, which would require liberal use of the de-optimizer and recognizing common sub-structures.

And with any non-trivial amount of optimization, it would lead to horridly looking HLL code. Compilation is a very "lossy" process when optimizations are turned on.