I think dramas historically showed episode titles a lot more than comedies. "Perry Mason" was always "The Case Of...", "The Twilight Zone" always had episode titles at the end of the show, and (maybe except for Season 1) at the beginning, and for its first few seasons, "Rawhide" showed episode names which usually were "Incident At/Of..." (the show's scripts were originally based on the actual diary recollections of a trail boss). And of course, there were all the Quinn Martin shows ("Tonight's Episode: Cloudy With A Chance Of Murder.") The one vintage sitcom I can think of that showed episode titles was "The Dick Van Dyke Show".
More recently, I know "Friends" episodes always had names ("The One With..."The One Where"), but I don't think they were actually shown onscreen. "M*A*S*H" episodes had names (not shown onscreen), and the 2 I can think of right now are the one where Henry left, "Abyssinia, Henry", and the finale, "Goodbye, Farewell, And Amen". I'm just one step from asking what stations aired "Duck Tales" in 1991, so I better knock off for now...