The much-anticipated return of ABC's "Who Wants to Be a Millionaire" has proved to be a profitable investment for ABC. Sunday's episode was watched by an estimated 26 million viewers and won its time slot against the season premiere of "The X-Files" on Fox, "Shake, Rattle & Roll" on CBS and miniseries "The Magical Life of Leprechauns" on NBC. Over at Fox, the new game show "Greed" also drew a fair share of money-hungry viewers last Thursday in its first outing.