1. "Hamlet" by William Shakespeare: Often regarded as Shakespeare's masterpiece, Hamlet is known for its philosophical themes, complex characters, and enduring popularity.
2. "King Lear" by William Shakespeare: Another Shakespearean tragedy, King Lear is renowned for its exploration of power, betrayal, and the human condition.
3. "The Importance of Being Earnest" by Oscar Wilde: This comedic masterpiece is noted for its witty dialogue, social satire, and exploration of identity.
4. "A Streetcar Named Desire" by Tennessee Williams: Considered a classic of American drama, this play explores themes of desire, conflict, and the fragility of human relationships.
5. "Death of a Salesman" by Arthur Miller: This Pulitzer Prize-winning drama delves into themes of failure, disillusionment, and the American Dream.
6. "The Cherry Orchard" by Anton Chekhov: Chekhov's play is known for its insights into human nature, social change, and the decline of the aristocracy.
7. "Waiting for Godot" by Samuel Beckett: A key work of the absurdist theatre movement, Waiting for Godot presents existential themes through its enigmatic characters and seemingly endless waiting.
8. "The Glass Menagerie" by Tennessee Williams: This semi-autobiographical play explores themes of memory, regret, and the power of illusion.
9. "The Seagull" by Anton Chekhov: Chekhov's play delves into themes of art, creativity, and unfulfilled desires.
10. "Les Misérables" by Alain Boublil and Claude-Michel Schönberg: A musical adaptation of Victor Hugo's novel, Les Misérables is known for its powerful storytelling, memorable music, and social commentary.
Ultimately, the greatest theatre play is a matter of personal taste and can vary among individuals and cultures.