Jon Cryer plays Lex Luthor in the current CW Supergirl series.  Michael Rosenbaum was the Smallville Lex. 

Cryer's Luthor is only sporadically used the show, which I suspect has a lot to do with how he is portrayed.  He is basically the evil, unconflicted Lex Luthor that wants to kill Superman and Supergirl, lacking any remorse, without any nuance or complexity.  But since he's been limited to guest appearances, he doesn't need to be anything more complicated than that.  Rosenbaum's Luthor definitely had more of an arc.  Initially presented as a well-meaning fellow with a dark side and daddy issues, his progression to the villainous Luthor was not unlike Anakin's turn in Star Wars.  Rosenbaum Luthor is a villain, but we are also meant to pity him for the tragic way he fell.  There were more than a few episodes that explored the idea of nature versus nurture and whether Lex would have turned out to be a decent guy if only he had better parents.