So Strange...I was just watching this movie this Saturday night...great minds truly think alike.
I preferred Russell in Tombstone, because he looked more like Earp, and also because he showed some humor when there was some to be shown. Sam Elliot and Bill Paxton were also very well-cast for their roles. Costner never smiled convincingly even once in Wyatt Earp, and his brothers were barely mentioned.
Costner is learning to act as part of a CAST, by the way...Open Range, though long on plot and character development, was outstanding. I haven't seen Costner act so well in a movie where he wasn't the central character since Silverado (which for a pure "Western" Western, has got to be one of the most fun movies ever made.). The Untouchables was a good movie, which Sean Connery (quietly and justly) stole, but it couldn't have been any further from the truth. Elliot Ness was not a role model in real life.
Costner is a fine actor in role written for or suited to his being the main character, and showed himself as smart enough to get himself out that rut. Look for great things from him in the future.
Looking back on Tombstone, Kilmer's Holiday was perfect. He was robbed of a nomination for that role.
"Look Darlin', that there is Johnny Ringo, the fastest pistoleer ever..."