not a hacker, but as an outsider i often get annoyed at the sort of paler colors used in hacks (like in liquid crystal), but i don't think that necessarily makes a game bad (because, for example, dark rising uses that type of tileset and idk why but it felt like it fit a lot more into the game).
I love to try out Fan Games and ROM Hacks and follow lots of them through this platform.
What I like the least is spritework. Beyond not being artistically inclined, I just can't be bothered to use those pixel editing software. I'd rather ask someone who's better at it to just get it done quickly and neatly and give them the credit; win-win.