Chris Reeve, Tom Welling, Tim Daly - in that order.
I like Brandon Routh as a person and actor, but was never completely sold on his look or his mannerisms as Superman so he doesn't get in my top 3. Only have slight familiarity with the rest of them, but to me the 3 guys I named above really embody the fundamental aspects of the 'Superman' character - his strength, compassion, determination, reserve and physical presence.
were is Kirk Allen
But, now, after the Finale, Welling does count, even if he didn't before, because of this:For me personally:
Dean Cain
Tim Daly
Chris Reeve
George Reeves
Gerard Christopher
John Newton
Brandon Routh
and I'm sorry, but I just don't count Tom Welling. I loved Smallville at times, but the only way I could really enjoy it was to accept it had nothing to do with Superman... they just wanted it too.
I can't stand the Christopher Reeve movies, my Superman in live action is the one done by Dean Cain and the animated one by Tim Daily.