I'm probably the only one here with a contrarian view on these films.
Like someone said above, Tombstone is more a look at a specific point in Earp's life, whereas Wyatt Earp is more of a biographical look at Earp's entire life. I didn't actually see Tombstone when it came out, and in fact didn't watch it until years later. Yes, it was a damn good movie but I've nevertheless always preferred Costner's movie. Wyatt Earp was a real person, and Costner's movie did a great job at portraying him; I won't get into whether the portrayal was 100% accurate to Earp's real life persona, as I really don't know. This is as opposed to what I view as a more typical portrayal of the man in previous movies, including Tombstone - simply a lawman who gets into a beef between two warring families.
I loved the James Newton Howard score for Wyatt Earp. It has an epic quality comparable to John Barry's Dances With Wolves score or Howard Shore's work in The Lord of the Rings / The Hobbit movies.
I'll agree that Tombstone has the better cast in terms of known names for comparable parts - not going to include Gene Hackman from Wyatt Earp since the role of Earp's father was not included in Tombstone. Kurt Russell, Val Kilmer, Sam Elliot, Bill Paxton, and Powers Booth are the names I'm looking at, as opposed to Kevin Costner, Dennis Quaid, Michael Madsen, Linden Ashby, and Lewis Smith in the roles as Wyatt, Doc Holliday, Virgil, Morgan, and Curly Bill.
Oh, and minor correction for OP - Tombstone released during the holidays of 1993, with Wyatt Earp coming out late in June 1994.
