There are "flops" and "hits" and there are "successes" and "failures."
"Flops" and "Hits" are purely objective financial terms having to do with a show paying back its original investment. If a show fails to recoup, it is a "flop" no matter how great it is or how long it runs (some flops have run 4 to 5 years and never managed to turn a profit). "Hits" return their investments. Period.
"Successes" and "Failures" are purely subjective assessments of a show's value critically and artistically. There are plenty of hits that I would consider artistic failures and plenty of flops that were artistically successful. Most of Sondheim shows come to mind as examples of the latter -- I actually got this distinction between "flop" and "success" etc.... from 20 time Tony winner Hal Prince. He called most of the Sondheim shows he produced and directed "successes" -- they were what he and Sondheim wanted them to be -- but, he was also clear that most of them were flops (Company and Little Night Music turned a profit; Sweeney closed as a flop, but over a decade later, according to Prince, it FINALLY paid back its original investment so it can now be termed a "hit)."
"What a story........ everything but the bloodhounds snappin' at her rear end." -- Birdie
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"The Devil Be Hittin' Me" -- Whitney