Are you one of those retro fans who are actually capable of hacking and modifying games for old consoles, or do you want to become one? Why bother at all!
First of all, no matter how good your game is, someone will most certainly not like it.
If you make the game too difficult, someone will most certainly not like, but! if you make the game too easy or normally difficult someone will most certainly again not like it, claiming it is too easy.
You will even come across such paradoxes, that a fairly easy game will be regarded as too difficult by some and yet too easy by others. So to conclude: no matter the actual difficulty, you'll always get the difficulty of your game wrong.
If your designed levels are based on exploration, someone will certainly call your game boring due to so called Backtracking. If you then decide to change that onto the better, don't bother, your edited levels, which will remove the backtracking, will certainly be called too Linear, which is apparently again no good. So to conclude: no matter the actual exploration factor, you'll always get the level design wrong.
If you decide to change the gfx, someone will certainly not like it, since they will claim the old gfx was better and the new one is too radical, custom made and thus no good. If you however decide to keep the original gfx, your game will be called "vanilla". So to conclude: no matter what you do with the gfx, you'll always get it wrong.
If you decide to implement special new music engine called MSU-1, don't bother, someone will definitely like SPC better. If you however keep the SPC, they will certainly tell you, that you are out of date, not switching to MSU.
If you mannaged to actually finish the project, you will come across painful testing. You will test and test and test, but why do you bother, you will certainly miss a bug or two, and when a player will come across such a minor problem, he will call your game (which you painfully tested for bugs) bugged. So why bother: no matter how much debugging you'll make, someone will still call your game bugged.
No matter how much you will check the grammar of the texts in the game, you'll surely miss out something. So why bother: no matter how much you will try to find spelling mistakes, someone will most surely find some and call your game a spelling horror and then add: this is common in those "custom made fake games".
If you designed your game to be used with save states, someone will call this a poor design, if you designed your game to be used without save states, they will use them anyway, making your game too easy - again. So why do you bother?
No matter how much TXT info files you will write, someone will surely patch your game to the false original rom, claiming you did a poor job with your game, since it doesn't load.
No matter how much TXT info files you will write, someone will surely patch your game to the false original rom, claiming you did a poor job with your game, since the game crashes in the middle of the playing. If you tell them to obviously check the CRC before playing they will tell you, that they've never heard of such a thing. So why do you bother?
If you tell them, to patch to a non headered rom, someone will definitely patch to a headered rom and claim your game to be bugged or not working, not knowing what went wrong.
If someone by somesort of a miracle likes your game, they will surely abuse it, by putting it onto the cart and sell it for money, making you look like the bad guy, who promotes piracy, since you are making "hacked" games. Your txt warning of "fair use" and "personal use" and "no rom or cart distribution" would be like an ant yelling at the supernova.
No matter how "just" your intentions are, in the eyes of the authors who made the original game, you are a thief, who just abused their intellectual property. In their eyes you are a pest, who is responsible for illegal cart distribution, since you made it happen. You can also be regarded as the person, who gave their game a bad name, since your game can never match the original one. In their eyes you are thus producing illegal derivated work of a poor/false quality and trying to benefit of it. So why do you bother?
That's what you get because you have programing/level designing talent/non talent and simply like an old game. Maybe being smart is not a good thing at all.
Make your life complete and quit romhacking to save your self a lot of trouble. Don't bother.