For about half the first season of B5 I thought Michael Garibaldi was played by Bruce Willis and wondered how they got such a big name star for a relatively small Sci-Fi show. I think eventually I looked at the credits and realized it wasn't Bruce Willis, but instead this actor Jerry Doyle, who looked and sounded a lot like Willis.
Only Jerry Doyle could act. I would see Bruce Willis in a show and think, "Why has Jerry Doyle gone all flat and expressionless? Does he have the flu?"
I met him at a DragonCon once a long time ago. Good guy.
Pretty much all of the B5/Crusade types I ran into were.
It seems like the ST people have better longevity.