I'm often pretty perplexed by the claims that Routh or Cavill were good in the role despite weak writing and yet that is how I feel about Dean Cain in Lois & Clark (though with him (and the other characters on the show) I think the writing was very uneven rather than overall weak).
Welling was strong (in the high school years), Cain was very strong and a close second but Christopher Reeve is the best.
George Reeves, though he had some good moments, I couldn't really get in to, his portrayal felt too old-fashioned and dated and vaguely talking-down even though I like other old and older movies and TV.