For me, a disappointing show has to have had promise in the first place,either because of the creatives,the cast, the ambition,etc. For that reason, some of the shows listed would never appear on a disappointed list(vs. a didn't like list, because I didn't expect much,e.g., Anastasia, Bullets, Rocky, Charlie.
In terms of real disappointments, I would cite:
-- Fun Home...expecting so much, bored the entire time;
-- Catch Me If You Can...what a waste of so many talented people's time
-- Promises, Promises revival. Miscast Chenoweth, seemed smutty in a way that it did not seem in its original production. Very disappointed.
-- Spiderman...JulieTaymor, Bono...disaster
-- A Doll's House, Part 2...great concept, well acted. Just not enough meat to me. Needed a play, not a playlet.
-- Follies Revival...I did not hate it. I just concluded that the Follies of my youth was a one-shot deal, with its weaknesses, e.g.,the script, masked by all the excellence everything else.
--Once. Actually enjoyed this for the first time at a tiny theater in Sarasota, Fl. I have concluded that the (whatever the name of the theatre it was in -- I think of it as the Royale,shoot me -- was just too large for the show(and I was pretty close).
-- The Front Page. I have loved other productions, so I will blame the director. It remained still-born until Nathan Lane arrived 2/3 of the way through the show.