Besides just being an awesome human being, Reeve was that rarest of gifts to us fans; an actor who "gets" and appreciates what Superman is all about. He made it clear he saw the role as a great honor and not an embarassment or something to "get his foot in the door." For Reeve, playing the Man of Steel was an awesome responsibility, and just to prove how well he "got" Superman, he behaved like one off screen, as well.
I could get long-winded here, but rather than take up space on these boards I decided to add a tribute to my site:
http://nightwing.supermanfan.net/editorials/reeve-rip.htmThat was a very moving piece, Nightwing.