I didn’t like The Empire Strikes Back when I was a kid, because I hated that the story wasn’t finished. Now it’s my favorite Star Wars film.
I never really disliked M.I.A., but I thought her music was kind of silly at first. Then I learned about her cultural background, and it all ceased being silly.
Let me guess: Flukeman?
For me, though “couldn’t stand it” is a little strong in both cases, I’d say it’s The Sopranos and Battlestar Galactica. In both cases, I saw the premieres, saw good stuff in them but was in a “we need to watch less TV” phase of my life and decided there wasn’t enough good stuff there to merit the investment of time.
Two seasons later, The Sopranos became the first show I got caught up on back episodes of via DVD and much later, Battlestar became the first TV series I watched almost entirely via Netflix.
I said for a while that I hated the Simpsons. I hadn’t really given them a chance at that point, and just sort of assumed, (based on the reputation they had in the mid nineties) that the show really was everything I like least out of Married with children, Family guy (though that hadn’t even started yet,) and other ‘proud to be offensive’ Fox comedy.
I don’t remember when I actually flipped on the Simpsons - probably sometime during the sixth season. I remember being very excited about the hubbub for finding out who actually shot Mister Burns. 
I’ve had good albums really grow on me, but I hated Flogging Molly’s Float album. Now, it’s replaced and shamed every other album on the list. (And that damn music video is so damn good, too!)
Ditto on Firefly.
Fining out alter that they released it out of order explained it a bit, but also the cowboy-North/South thing took me a while to get past.
Otara
Another former Seinfeld hater here.
I wouldn’t say it’s my favorite sitcom series, but when it first came out, Jerry’s on camera sniggering made me want to slap him, and I just found everyone annoying.
Now, I watch it and I see how well it was written, and everyone being annoying is the whole point of the show.
Horseradish, ginger (to a degree), and toasted seaweed.
As far as food goes, the first time I tasted A-1 on a steak I thought it was bitter and odd and didn’t like it. Strangely the next time I had a steak I felt like it was missing when it wasn’t there. Years later, I nearly always use A-1 with my steak, even if it is on the side for dipping.
I am pretty sure they put a narcotic of some kind in there.
FWIW, I’ve watched it many times. While I think it is really funny, it’s not really one of my all time favorites. I love Coen brothers movies, but The Big Lebowski doesn’t rank that highly to me.
I also didn’t like Firefly the first time I saw it, and am now among the biggest Firefly fans you’ll meet. It also took me multiple viewings until I liked River Tam as a character.
When I was younger I didn’t understand the appeal of Bob Dylan. I think I was focusing too much on the vocals, and perhaps also looking for lyrics that were deep, man, and which I could spend hours interpreting. I listen now and I hear the words of one of the great poets of the 20th century. I think I just needed to understand the ballad style.
Big Bang Theory.
The premise seemed stupid and insulting, then, since it was getting good word of mouth here, I watched the episode where Sheldon tried to befriend Kripke, to get a shot at…some equipment or other, I can’t remember what.
Loathed it. There were 2 bits that amused me - Sheldon insulting Howard, after he figured out an escape condition for the infinite loop in Sheldon’s friend-making algorithm, and Sheldon passed out after attempting rock climbing again, at the end.
I hated everything else about it. I hated Sheldon, I hated Kripke (who I didn’t know, at the time, was so minor a character), I didn’t much like Leonard, Howard, Raj, or Penny. The scene where Sheldon tried to befriend the little girl was just painful to watch. It was obvious where they were going to go with it, and it just wasn’t a funny joke.
Then, later, a friend talked me into watching some more episodes, and I came to put it on my list of can’t miss shows.
Still can’t stand a) that episode, or b) Kripke (who is like the worst elements of Sheldon grafted onto the worst elements of Howard with what minimal charm they have removed, and that damn speech impediment added). Everyone else grew on me, though.
I think you’re supposed to loath Kripke, though.
And WHill WHeaton.
Well, yeah, but I hate him being on screen, at all, not the way you’re supposed to hate him.
He’s not like Wil, who I would want to punch IRL (if he were anything like his character), but is FUN to watch. Any episode where Kripke’s there is just a chore to watch.
Mr. Ko started watching MST3K long before I did. I’d hear it in the background and remember thinking it was somewhat annoying. I got hooked after finally sitting down and watching a full episode (The Pod People, IIRC). Now it’s #1 on my list of all time favorite TV series.
I forgot about The Simpsons. I had the same experience as chrisk, not caring until season six.
I also remember my dad and brother bring quite excited about 2001 but I fell asleep two times when trying to watch it as a teen. When I sat down to watch it critically as an adult, I fell in love with it.
Hummus. I can’t stand chickpeas, and couldn’t imagine anything worse than a pasty dip made from satan’s testicles. Then one day in my late 20s, I threw all caution to the wind after a couple beers, and tried it. I can’t imagine life without the creamy, beige, lemony, garlicky goodness now.
Seinfeld and Gentle Giant (the band).
Green olives. For years, I couldn’t stand the smell of them, then about '98 or so, my parents had a bowl of them sitting out on New Year’s Eve. I kept eyeing them and thought… it’s been a while since I’ve tried one, so I did… And now I love them! Always have a jar of olives in the fridge!
I didn’t “get” The Big Lebowski the first time I saw it. Thought it was stupid. I saw it a few more times and it grew on me. It’s now one of my favorites.