I would have to slightly disagree with the two other answers. Instead of this being only in a joking manner, it can be serious or at least semi-serious.
I do agree with their definitions of what the phrase means, though, so I'm not going to re-define it here.
I've had gruesome movies put me off my meal, they "ruined it for me". One particular instance kept me from eating that same food for months, since it resembled what was on the screen and basically gave me flashbacks.
I've "ruined" songs for people by describing a funny alternate meaning to it, when they considered it serious, so they couldn't get my version out of their head when listening to repeat plays. I've ruined magic or movies by explaining the mystical aspect that drew someone to it. I've ruined advertisements for myself by realizing I don't need 99.99% of what they are about.
Most news shows have been ruined for me by their use of out of context soundbites, always showing only the worst news, pretending lies and political rhetoric are facts, or pretending that the news anchor or host knows better than anyone else and we should just believe their opinion. On the other side of that, I have found specific news sources that work hard to not be biased, show the whole story, are generally considered reliable by the large majority of people, and let me make up my own mind.
I've even had songs that were ruined for me by their own original singers, but were redeemed by another singer doing a remake. I may still not like the original, but at least the remake is still good.
When I was a little kid, my older sisters would try to get me to taste unsweetened baking chocolate when they made brownies or anything else that used it. After falling for it a couple times, it ruined dark chocolate for me, as well as my trust for my sisters. I will also hesitate to eat anything with powdered chocolate on it, but I still like chocolate in general. Even as an adult, I still hesitate to eat anything one of my sisters asks specifically me to try, especially while they are still making it.
There's plenty of leeway for something to be "ruined for someone" to be used in a humorous or serious way, as well as short term or long term. It can even be a targeted, specific instance of something being ruined rather than a broad dislike for everything related to that something. Just like most things with the English language, context is important here. And context can include non-verbal communication.
To go a little further, there's a similar phrase that you might run across: to be put off something. You could say that my sisters "put me off" dark chocolate by their pranks. It's a way to say essentially the same thing. This phrase, however, tends to be more of a long term or serious situation, but it can still be used for humorous or short term examples.