The hack rom of today is Pokemon Dream, here is a description from pokeharbor:
"Pokemon Dreams is a hack that takes place in a new region and tells a new story. The main character, a travelling trainer, arrives in the Solda region. They meet a boy in the small community of Thicket Town who aspires to be like his brother, the local gym leader. This is their journey through the region as they meet new characters and strive to become members of the Pokémon League.
This hack was created with a focus on characters and worldbuilding in mind. Despite the fact that it tells a linear story, the map is peppered with optional areas containing useful items and Pokémon to encourage exploration."
Features
8 Gyms, a Pokémon League, and postgame rematches are playable
All Pokemon through Generation 7 available
Small cast of 35 Fakemon brings the total to 844 Pokemon
New region with new story, characters, and battles
New music
Pokemon movesets brought up to date with Generation 7
Battle system updated to Generation 7 (Physical/Special split, Gen 6 type chart, Fairy type, etc.)
All mega evolutions are included, alongside some new ones
Dexnav
NPC trainers do not use healing items in battle
Trade evolutions now use stones instead
120 reusable TMs