I've often wondered about this change. Lyrically, "I Guess the Lord Must Be in NYC" is the right choice. But "Everybody's Talking" is what I heard when watching the movie in its release. I don't know if my initial experience has colored my preference (when I heard the LP, my reaction was "Darn, that should have been on the MC soundtrack), but emotionally I find "Everybody's Talking" fits the mood of the storyline if not the movie theme lyrically. I think the "wrong" choice actually makes Midnight Cowboy a better movie. There's plenty of NYC in the actual film. ("You don't need a soundtrack to tell which way the wind's blowing".)The original choice is a bit of Mickey Mousing (as the Hollywood types would say).