Last night's season finale of Lost had commercials for the new feature Superman Returns, which stars Kevin Spacey as Lex Luthor. The episode also featured Clancy Brown in his recurring role as a U.S. Army intelligence officer.
Clancy Brown has been the voice of Lex Luthor in various Bruce Timm produced animated series -- most recently, Justice League Unlimited.
On Justice League Unlimited, veteran voice actor Michael Rosenbaum provides the voice of The Flash. A recent episode had Lex Luthor's and the Flash's minds switched, so that Rosenbaum was essentially portraying Lex Luthor.
On the live-action series Smallville, Rosenbaum plays . . . Lex Luthor.
As Denis Miller once said, "It's all as interrelated as an Appalachian Mining Town."