One thing about those two theme songs I mentioned: though you hear the full versions over the long closing credits, the actual opening sequences are only about 20 seconds each — about the time a half-hour comedy has for a title sequence today. So it really is possible to do a memorable main title in a very short amount of time, and more shows should really be coming up with memorable, easily-identifiable title sequences (preferably actual action, rather than still pictures, which just don’t have the same effect: Dick Van Dyke actually started with still pictures in the main title, and switched to the ottoman opening in season 2).
http://www.youtube.com/watch?v=QqIyjLxwk-s
I’m also very partial to Hagen’s opening theme for season 1 of That Girl; they rearranged the theme every year after that, and it never sounded as good as the joyous, New York-ish sound of the first season:
http://www.youtube.com/watch?v=M9rapJrbNRA