Gunsmoke would have to be the best and most venerable of TV Westerns. Just about anybody who was an active character actor during its run appeared on the series.
As a bit of trivia - William Conrad was the radio Matt Dillon, but his appearance was not that of a leading man and so when the TV series evolved, he was dropped.
His voice was just right for radio - everyone may remember him from Cannon and Jake and the Fatman.
Cheers -
Jay