I ended up with 21.
Wayne starred in a bunch of them (7) but other multiple appearances in starring roles included Ben Johnson (5), Charles Bronson (4), John Carradine (3), Jimmy Stewart (2), Charlton Heston (2), Steve McQueen (2), Brian Keith (2), Rick Lenz (2), Michele Carey (2), James Coburn (2), Harry Morgan (2), Ward Bond (2), Andy Devine (2), Edmond O'Brien (2), Simon Oakland (2), and Warren Oates (2).
The Top Twenty-One (in no particular order) are:
Stagecoach (John Wayne, Claire Trevor, John Carradine, Andy Devine, Donald Meek)
Once Upon a Time in the West (Charles Bronson, Henry Fonda as a very bad villain, Claudia Cardinale, Jason Robards, Woody Strode, Jack Elam, Frank Wolff)
Ride the High Country (Randolph Scott, Joel McRae)
The Magnificent Seven (Yul Brynner, Steve McQueen, Charles Bronson, Robert Vaughn, James Coburn, Eli Wallach)
True Grit (John Wayne, Kim Darby, Glen Campbell, Robert Duvall)
Scandalous John (Brian Keith, Alfonse Arau, Michele Carey, Rick Lenz, Harry Morgan, Simon Oakland)
Chato's Land (Charles Bronson, Jack Palance, James Whitmore, Simon Oakland)
The Man Who Shot Liberty Valance (John Wayne, Jimmy Stewart,Vera Miles, Lee Marvin, Andy Devine, Edmond O'Brien, John Carradine, Woody Strode)
The Wild Bunch (William Holden, Ernest Borgnine, Robert Ryan, Edmond O'Brien, Warren Oates, Ben Johnson)
The Shootist (John Wayne, Jimmy Stewart, Lauren Bacall, Richard Boone, Hugh O'Brien, Ron Howard, Scatman Crothers, Harry Morgan, John Carradine, Sheree North, Rick Lenz)
Nevada Smith (Steve McQueen, Karl Malden, Brian Keith, Arthur Kennedy, Suzanne Pleshette, Martin Landau)
Rio Bravo (John Wayne, Dean Martin, Ricky Nelson, Walter Brennan, Angie Dickinson, Ward Bond)
Hang 'Em High (Clint Eastwood, Pat Hingle, Inger Stevens, Ed Begley, Ben Johnson)
Breakheart Pass (Charles Bronson, Ben Johnson, Richard Crenna, Jill Ireland)
Will Penny (Charlton Heston, Joan Hackett, Donald Pleasence, Lee Majors, Bruce Dern, Ben Johnson)
Gunfight at the O.K. Corral (Burt Lancaster, Kirk Douglas, Rhonda Fleming)
Hondo (John Wayne, Geraldine Page, Ward Bond, Michael Pate, James Arness)
The Alamo (John Wayne, Richard Widmark, Laurence Harvey, Frankie Avalon, Patrick Wayne, Linda Cristal)
Silverado (Kevin Kline, Scott Glen, Kevin Costner, Brian Dennehy)
Major Dundee (Charlton Heston, Richard Harris, Jim Hutton, James Coburn, Senta Berger, Brock Peters, Warren Oates, Ben Johnson)
The Gunfighter (Gregory Peck, Helen Westcott, Millard Mitchell, Jean Parker, Karl Malden)
