Lol. Almost everyone on this site (especially since I know plenty of you are in your mid-30s and some in the 40 plus range) will be dead before NES games enter the public domain. 

This is super interesting to me. So help me understand, because I’m unaware of the legal precedent. Even if the assets are built from scratch, they’re still designed to replicate the characters, backgrounds, level designs, etc. of a copyrighted property, right? And the game still bears a trademarked name.

I understand that Nintendo might not bother because it’s small potatoes — although the level editor functionality could cut into Super Mario Maker’s domain — but I don’t understand how the home-grown assets create a legal loophole.

I think creations that were released after 1977 will only enter in public domain 70 years after the author's death. Considering that Miyamoto has around 20 years or more until his last breath, Super Mario bros will enter in public domain next century.

Unless we manage to outlive a tortoise lifespan then I don't see anyone here witnessing that or even having the cognitive ability to react to that

That looks awesome.

The main reason for copyright infringement is that you are enriching yourself on the work of others - which doesn't apply if it's free. This is doubly so if the assets are home-made and if it uses a different engine, which in case they look like the original ones can be considered reverse-engineered, which is mostly legal (For instance, it's how AMD copied Intel's 386 and 486 designs in the early 90's even though Intel didn't grant them a license for the chips. Intel tried to protest, but to no avail). At that point only the level design can still be considered copyrighted, otherwise it has become more of a trademark infringement (main characters and game titles are often also trademarked) - which again is more difficult to shut down if it's free.

Btw, this isn't the first SMB remake like this. I was looking for this in my first post but I didn't have the time to look for the game I originally meant to post there: Super Mario Bros. Crossover (though no visual upgrades in this case), which like Abobo's Big Adventure was made in Flash so they're a bit difficult to play nowadays but once you get past this limitation they're perfectly playable games.

However, like you said, the level editor might get them into trouble depending on what is possible to create with it or if people can introduce their own assets - which can bring in copyrighted assets and then get shut down due to them.

They've also taken a hands-off approach to the Mother 3 Fan Translation, since they don't plan on releasing it themselves.

That's is not true at all. Copyright infringement can apply when there is no profit being made. It is usually up to the discretion of the Copyright holder whether they want to pursue litigation or not.

That is for works by a single creator, such as an author. If it is collaborative work such as film and video games, it is 95 years after release. So in 2080 actually.

Which is an absurd amount of time if you ask me. Super Mario Bros. should already be in the public domain imo.

Copyright can be selectively enforced. Any company can copyright claim fanart if they wished, but that's bad press for absolutely zero gain. Nintendo lawyers tend to strike when something gets too much media attention and/or has overlap with something they are planning in the future themselves.