I have the feeling that over the past years, we've started seeing more TV shows that are either sympathetic towards Hell and Satan, or somewhat negative towards Heaven. I just watched "Hazbin Hotel" today, which isn't too theological, but clearly is fairly negative towards Heaven.
In "The Good Place",
Spoilers for The Good Place
the people in The Bad Place end up pushing to improve the whole system, whereas The Good Place is happy to spend hundreds of year not letting people in.
"Little Demon" has Satan as a main character, and he's more or less sympathetic.
"Ugly Americans" shows demons and Satan as relatively normal, and Hell doesn't seem too bad.
I only watched the first episode of "Lucifer", but it's also more or less sympathetic towards Lucifer.
I have a few more examples (Billy Joel: "I'd rather laugh with the sinners than cry with the saints", or the very funny German "Ein Münchner im Himmel", where Heaven is portrayed as fantastically boring), but I won't list them all here.
My question is: how modern is this? I've heard of "Paradise Lost", and I've heard that it portrays Satan somewhat sympathetically, though I found it very difficult to read. And the idea of the snake in the Garden of Eden as having given free will and wisdom to humanity can't be that modern of a thought, even if it would have been heretical.
Is this something that's happened in the last 10 years? Are there older examples? Does anyone have a good source I could read?
Note that I don't claim Satan is always portrayed positively, or Heaven always negatively :).
It's pretty modern if you mean popular, although the idea itself is REALLY old.
Rather than going into specific examples because there are a lot of them (especially in gaming and TV), I'd like to say my piece on cliches.
Basically, cliches come to exist because the cliche trope is a really good idea.
"The Butler did it" as a murder mystery trope is a fantastic idea because some people with too much money will use the protection money affords them to mistreat their employees, providing a great motive you can build on to create a great story with relatable morals and characters. It sets up a character with perfect motives, means and a reasonable position of trust to avoid suspicion.
Similarly, "Hell good, Heaven bad" is a fantastic trope because it lets you step back and analyse things like the negative impacts of religion and how authorities (and the bible) will portray themselves as good regardless of their actual actions. Plus of course there were periods of time where people were told doing virtually anything that didn't fit into an extremely narrow worldview meant you were going to hell. You know, stuff like basketball and Dungeons and Dragons.
Now, the problem with cliches is when someone sees a popular idea that's also a very good idea, but doesn't understand why it was a good idea. As a result, when they use the idea, it rings hollow at absolute best, and that kind of terrible execution of something that's already known and popular tends to be especially disappointing. I think the best example is The Hunger Games, which absolutely defined young adult dystopian fiction for years because it showed how the media industry mistreats its workers, and Alleigant, which used a lot of ideas from Hunger Games (and some other things) without actually understanding the ideas.
(TLDR: Hunger Games has a love triangle as a prominent plot element, but the actual reason is that it's perpetuated by the media pretty much on pain of death for Katniss so that she can entertain the viewers. By contrast, Alleigant also has a love triangle but the triangle IS the plot element and the author bends over backwards to make it happen despite the fact none of the characters really feel like they're suitable for it)
Anyways, cliches aren't bad but you need to know how, why, and when to use them in order to actually fulfil their potential, and the heaven-hell one you've mentioned above is no exception.