ACTOR Milo O'Shea has been in the business for many years but has his first big hit playing Father Farley in "Mass Appeal," which opened last night at Ford's Theatre. O'Shea, who began his career as a music-hall comedian, also can be seen as the judge in the movie "The Verdict." O'Shea picks the productions he has enjoyed most, all of which are two-character plays:

1. Staircase: "With Eli Wallach. My first time on Broadway and I was nominated for a Tony for it."

2. I Do, I Do: "A musical written by Tom Jones and Harvey Schmidt, who wrote The Fantasticks. It's a favorite because I met my wife, Kitty, while we were performing in it at the Dublin Theatre Festival."

3. Do You Know The Milky Way? "Also in Dublin. It was directed by Michael Lindsay-Hogg, Geraldine Fitzgerald's son. We've been friends for a long time."

4. Mass Appeal: "A two-character play that was very important to my career. Plus, it got me a Tony nomination and was directed by my friend Geraldine Fitzgerald."

5. O'Shea didn't pick a fifth favorite, but listed several plays which became musicals (in every case he performed in both versions): "Pygmalion became My Fair Lady, and I did the national tour of that; Playboy of the Western World became The Heart's a Wonder; The Four-Poster became I Do, I Do; and Juno and the Paycock became the musical Darling Juno."