Well, let me think. I like Gogol’s The Government Inspector. It is his most famous play and probably his best work in general. I like The Cherry Orchard and Three Sisters by Chekhov, those are worth looking into. Leo Tolstoy’s The living Corpse and The Power of Darkness are pretty good. And I actually really like Mikhail Bulgakov’s writing and his plays are not an exception. A lot of his work was banned in USSR, but now he is considered one of the greatest writers of 20th century. I saw his play Flight when I was in St. Petersburg a year or so ago and was not disappointed. It’s a play set during Russian Civil War and it was banned for a long time because it depicted both sides of the conflict. Also, he wrote a play called Ivan Vasilievich which was adapted into an absolutely great Soviet movie called Ivan Vasilievich Changes His Profession commonly translated as Ivan Vasilievich: Back to the Future. It’s a comedy in which a Soviet citizen Ivan Vasilievich and Russian Tsar Ivan IV Vasilievich, more commonly known as Ivan The Terrible, switch places and have to survive in a different time period. Both the play and the movie are great, but I don’t think the play was translated into English.
Edit: To answer Pandora’s question, I like musicals, but I, unfortunately, didn’t get a chance to see many of them. Basically, I think that musicals can bring something extra and different to the table. Some of them are great, some are not so great, but overall I’m happy that they exist as a form of expression.