Here are some depictions of the big guy by Neal Adams...
Superman #252, June 1972.
Superman #250, April 1972.
Superman's Girl Friend Lois Lane #93, July 1969.
Superman's Girl Friend Lois Lane #95, September 1969.
World's Finest #209, February 1972.
Below is Adams' wraparound cover to All-New Collector's Edition #56, Superman vs. Muhammad Ali, 1978. And below that is a black and white stat of the original art. How many celebrities can you spot on the cover? Partial list here.