When is media notable enough for an article?

Hey, I'm only 11 days late!...
...
Anyways, to answer OP's question, the things that we scrutinize most heavily are internet media. I'm reluctant to put a hard cap on subscriber minimum or stuff like that because there's always exceptions, but it really, really should be someone/something that a lot of people on the internet know, and not some obscure user with a hundred subscribers. Ideally everybody would ask before writing stuff on internet media, but people just go ahead and do it anyways, so all we can do is delete the irrelevant ones and say sorry to the people who wasted their time writing them.

Dubs are also scrutinized pretty hard - as it states in the rules, if it's not an English dub or the original language of the media, you need to get approval before writing a page, and you should have a very good case lined up for why it's important.

Now here's a rundown of some of the other categories:

-Movies: Big-budget stuff is obviously okay. Independent films and short films are usually fine, just be sure it had at least a little bit of actual production value behind it and was made by real filmmakers, not something that's just a glorified youtube video by a group of friends with a camcorder.
-TV Shows: If it aired on national TV in any country, that's a pretty safe bet that it's good. Most TV is fine, unless it's like a completely unknown public access show or a talk show that only aired in one random city like Cochrane Alabama or something.
-Literature: Should generally be a published book, or something written by a well-known author. Self-published stuff is generally held to the same standard as internet media in that it should be well-known or connected to something well-known.

I honestly feel like the rest are pretty common sense... if it was made by a company, or made by a small group of people and got reasonably popular. For the recordings of real incidents, it should be an incident that's news-worthy on some level. For video games and music, the current bar of entry for making them is way lower than it used to be, so there's great stuff made by individual people that blows up on the internet. There's also a ton of complete trash that isn't worth a second thought. I hope most people here can spot the difference between Undertale and Really Scary.

Some stuff is a really obvious "yes" or "no". As a general rule, if it either has a wikipedia page or was made by someone with a wikipedia page then it's likely okay - that's always not a requirement though. The number of concrete sources you can find to write your article can also be a pretty good indication of whether or not it's something of interest. But there are always exceptions and grey areas, so as virtuaboi said, if you have any doubt of your article's eligibility, there's no harm in asking.