I think it was not even 2 1/2. It was 2. The Morocco and the Helen Hayes.
I experienced the single greatest evening in the theatre in my life at the Morocco. It was The Moon for the Misbegotten with Colleen Dewhurst, Jason Robards, and Ed Flanders. So the theatre will always be special to me. Also saw the original The Price, the original Butley, Julie Harris in at least three shows that I can think of (In Praise of Love, 40 Carats, and And Miss Reardon Drinks a Little), Edward Albee's most under appreciated play, The Lady from Dubuque with Irene Worth), Da, Comden and Green, Pulitzer winning The Shadow Box, and quite a few others. It was one of the playhouses that was always in demand. But, truth be told, it was possibly the ugliest and most uncomfortable theatre on Broadway, so I have great memories, but don't miss it as a theatre.
The Helen Hayes, on the other hand, was a jewel box. I used to love to see shows at the theatre because it was so intimate and just beautiful, starting with its facade. I saw my first show ever there...Mary Mary; and, while I was too young to enjoy it (I think I was 13), I still have vivid memories of that day.
I had some great moments in the Helen Hayes that I will also always cherish, The Prime of Miss Jean Brodie, The Royal Family, Hadrian VII, 6 Rms Riv Vu, Crown Matrimonial, The Crucifer of Blood, A Touch of the Poet, and the list too goes on.
The issue that I always have when this topic comes up is that the Broadway time period during which these theatres were torn down was pretty awful. Times Square at night was almost deserted other than 7:30 to 8, and it was never that crowded then, since so many theatres were empty a lot of the time. The Marquis was just one of the things that contributed to the re-birth and health of the theatre district. And the drive towards musicals meant that the smaller straight play theatres would have been harder to fill. While I can think of two musicals the Hayes had, both were very small.
So, on balance, I miss both theatres, but much prefer the health and liveliness of the Broadway today vs. the period when they were torn down. I also miss the Mark Hellinger a lot more.
The thing I actually miss the most about change in the area is the closing of all the great movie theaters. When those live theatres were torn down, there were still movie theatres with vibrant marquees operating in the same general vicinity. Perfection for me would be some of those theatres to still be operating with their gaudy marquees and continuous performances. If I could have one or the other, I would do without the Morocco and Hayes in order to have the NY Paramount and Loews' State and Capitol and Rivoli. I personally think their loss was worse than the Morocco and Hayes.