I can't think of many. My first exposures to GYPSY, THE MUSIC MAN, and MAN OF LA MANCHA weren't great, and now I quite like all of them.
But my biggest turnaround has been SUNDAY IN THE PARK...
I got the VHS when I was maybe 14, after falling in love with ITW, as so many of my generation did.
It took two or three years before I even got through the whole thing.
Oftentimes, I'd put it on and fall right to sleep.
It's now my favorite Sondheim show and easily sits among my favorites overall.
For the most part, I've had the opposite experience, where I turn on shows that I once loved, which I chalk up to the follies of youth.
CHURCH DOOR TOUCAN GAY MARKETING PUPPIES MUSICAL THEATER STAPLES PERIOD OIL BITCHY SNARK HOLES