Many people really do want to create a great ROM hack that will be inspired by nearly everyone in most of PC. So if anyone is aiming to create one ROM hack that everyone will be wow'd about, here's what many should do.
First of all, a ROM hack has to be made with graphics that is not the generic ROM base graphics, by that... I basically mean the graphics that are normally on a FireRed/LeafGreen or Ruby/Sapphire/Emerald ROM. Now surely GameFreak doesn't re-use the graphics on more newer ROMs these days do they? Take a look at Diamond/Pearl for instance and compare it to Platinum. You'll notice how the textures are different, and that shows how things can be revamped and not re-used, the only time when GameFreak did re-use graphics is when they made Pokémon Emerald, which they only edited the normal field grass (not the grass with the wild Pokémon in it though). The best thing everyone should do... is create their own tilesets and textures from scratch, that is one way to create tilesets and textures that can truly revolutionize the appearence of a ROM hack. You can use other people's ones that you've found in the ROM hacking resources, as long as you give credit to them when you use it. After all, a generic FireRed/LeafGreen Ruby/Sapphire/Emerald original tileset really does make the appearence of a ROM hack look boring. Hence this is why most ROM hackers change the tilesets completely.
Next up is the characters, Pokémon and object sprites. Surely if you're looking to make a ROM hack not look anything similar to the original ROM bases, the best way to doing it... is changing the sprite to look different to that of the original ROM base. Technically I would consider changing the sprite to look totally different from the ROM base and the Nintendo DS generation ROMs (which I mean by 4th and 5th generations), what I think of usually is creativity. Though it's not like anyone has to do it or anything, you can use the sprites from the NDS generation ROMs, but it's always best to make them from scratch. Like for instance, for an item you might as well have a different sprite for potions or any other types of medicine, so you can see what it really is. Changing a backsprite for any of the characters or Pokémon is also a great way of making a ROM hack look so much better as well as the overworld sprites.
Making up a storyline for a ROM hack is one of most easiest of all things. "Why is that?" you ask? Well because all you basically have to do... is type in your ROM hack thread. xD As for editing the whole intro would also be a great idea along with changing how you enter your name or removing the part where you enter your name, that is if you know how to. And I don't basically know how to yet either. It probably would require ASM hacking. It also great to change the titlescreen completely as well, changing it completely may also require some ASM hacking to change the animation and stuff.
ASM, one of the things that can revolutionize a ROM hack. ASM stands for "Assembly", one of the things that can be edited and replaced in the coding. There is a tutorial on how to use ASM to create for a script in the game, but I'm not sure if there's one about changing the intro completely or something like that. We may need to research even further into this.
There is one thing that people do not like in a ROM hack, and that is none other than the bugs, glitches and errors. Some can prevent people from progressing in the ROM hack, while others can screw up certain conditions or crash. Anyone who experiences any of that always posts it in author's ROM hack thread or PMs the author of the bug or glitch in the ROM hack. You can also use a debugging emulator to identify the glitch or the bug in the ROM hack and show the breaking point to the ROM hack author, which then helps them research further into it, which then can help them learn new ways of editing stuff and possibly creating a tool for it.
Audio... one of the things that we all hear from our ears, correct? Something we all think we can totally change the way we hear a certain song or sound effect. The best thing that can be done in this manner, is that anyone can simply insert a song into a ROM hack and test it out, when anyone does this, you can also change the offset for the soundbank that is used. If you're creating a ROM hack with very creative tilesets, then you would also need very creative music along side it as well. What I'd technically do is create my own songs from scratch for a ROM hack rather than trying to use what is used in a different game or a different generation of Pokémon. Usually it's only necissary to insert music from other games of Pokémon if you're including a region from a different Pokémon game or something. But here's one thing that makes a ROM hack less interesting: using the songs that come with the ROM base (eg. Ruby/Sapphire/Emerald and FireRed/LeafGreen) that you're using to create the ROM hack. The reason to this is because it makes it sound too generic and just feels like you're playing the ROM that the ROM hack is based off.
This is all the advice about the keys to creating a very creative ROM hack. Good luck! ;)
~Davin (aka Platinum Lucario)
