Check out the top 40 magazine covers of the last 40 years. The problem is that there is a stark difference between design and semantic "best", with (unfortunately) too much weight placed on semantic. My re-ranking would be:
  1. People Mar 4, 1974 (Mia Farrow)
  2. Blue Oct 1997 (Diving guy)
  3. National Geographic Jun 1985 (Female Kurd in red)
  4. Interview Dec 1972 (Christmas dual-spread)
  5. Playboy Oct 1971 (Black bunny)
  6. National Lampoon Jan 1973 (Shoot the dog)
  7. Economist Sep 10, 1994 (Camels got hump!)
  8. Harper's Bazaar Apr 1965 (Pink Polka-head)