Scott Glenn
Some posters have commented unfavourably on this film because it has a cast with few western regulars. I've never seen that as an issue myself and of course Kevin Costner went on to make some fine westerns at a later stage.
As far as I know, Silverado was Scott Glenn's only western, yet I feel he quietly just about stole the show as Emmett. IMO he had the looks and charisma to really succeed in this genre and I'm surprised he didn't do more, though I suppose there wasn't a lot of westerns on the go at the time.
I'd be interested to see what others think.