I would have to say John Carpenter's theme for HALLOWEEN. But I love lots of film music. Most films today have mediocre to no main title themes, even though they may have nice scores, overall. Some other favorite main title themes are:
SUPERMAN - John Williams
HAWAII - Elmer Bernstein
THE OMEN - Jerry Goldsmith
NORTH BY NORTHWEST - Bernard Herrmann
GONE WITH THE WIND - Max Steiner
A PATCH OF BLUE - Jerry Goldsmith
THE TAMARIND SEED - John Barry
THE WORLD OF HENRY ORIENT - Elmer Bernstein
just to name a few.
ConvinceMe2 is dead. Long live BrendanStryker!