It depends. Are we talking about the material or a particular production?
Great material touches an audience whether it's cast with Broadway professionals, TV actors, or capable amateurs. Here are great stories with top-notch script/scores:
1. Sweeney Todd 2. Gypsy 3. Chicago 4. Fiddler on the Roof 5. Into the Woods
On the other hand, if we are talking about productions here are some that hit me the hardest. These were all a unique combination of acting, directing, and design that were perfection in their time, but now just a memory. All productions were original Broadway casts.
1. A Chorus Line - The original cast was devastating. There was actual psychic pain on stage in the almost Hunger-Games-like setup. All wrapped in state-of-the-art choreography and theatrical conception. I went back and saw it twice in a month. Years later I saw the National tour and was very disappointed that the tension had drained from the proceedings and it had become just a lot of young talent stepping forward to do their big number.
2. Sweeney Todd - It says a lot that I left Sweeney not thinking of murders, blood, and cannibalism, but rather justice, morality, and the highest level of music and lyric writing I had ever experienced in the theater.
3. Dear Evan Hansen - Ben Platt had me from his opening monologue through each step as the stakes got higher and higher and you held your breath waiting for the house of cards to come crashing down.
4. Falsettos - I had seen a lot of musicals and a lot of love songs, but seeing Marvin in bed singing "What More Can I Say" to the sleeping Whizzer it hit me that I had never seen a man sing a tender love song to another man before. Moments like that kept me reaching for a Kleenex through the whole show.
5. Company - My first Sondheim. Dean Jones as Bobby - no one else in that role has touched me as deeply as Jones. He needs and wants so much, but at the same time is so afraid to go after it.