ROM Hacks that genuinely improve the base game?

[Your_Homie_Gale]

Pokemon Crystal Clear and Yellow 151 for a complete pokemon experience that doesn't change the pokemon stats or movepools making them compatible with other games. Thanks to PKHex I was able to transfer my pokemon to later gens without much issue. There are other pokemon hacks that change a few things, like Red ++, but they're too different from vanilla. Crystal Clear changes Crystal so much from vanilla, but the pokemon themselves are kept the same. Only difference is how to obtain them. Too many improvement hacks add new pokemon, change their stats, or make them more difficult; which aren't bad, in fact they're usually 9/10s, but I just prefer vanilla.

 

[Bakuma1997]

7th Saga: The New Class

Recently started it after reading the Review of the vanilla game, i tried both the Redux and plus ones, but they felt...kindaa meh

Then i tried the patch, i can only say... satisfied

Rather than a bunch of role-less blobs , the game aims to make the playable classes a single class focused moveset based on Final Fantasy 1 (The elf is a black mage, the devil is a thief, the knight is a red mage, ETC), with the black and white mages being nukes or inmortality inducers at the cost of being tissues, while the rest can hit like trucks, but their magic is lacking

Is made with Redux as a base, so if you liked it, you can get all the goods of that one, only flaw is that since headering differences made them incompatible, you can't use the name patch, so i have to guess what item does what with a crummy contraction

 

[Ikagura]

I've tried quickly Super Mario Kart with a full screen hack, it doesn't strictly improve the game but it's a nice hack.

The only down sides are that you'd forfeit the mini map and back view.