ITT: Add a single feature or make a single change that would drastically improve the quality of a video game of your choice.
I'll start with a few of mine...
1. Sonic Chaos (MS/GG) & Sonic Triple Trouble (GG): In this duology, known as Sonic & Tails in JP, the Chaos Emerald system from the previous 8-Bit Sonic duology, where you explored and just found them in levels, was ditched in favor of the Mega Drive styled special stages... but exploring to find them was way more fun, this should've stayed.
2. World Cup Italia '90 (MS): I'm quite fond of the way this plays football, but having only 8 players on each side instead of 11 is a bummer, but that clearly has been done due to the small pitch... a big pitch like SWOS, or even the 16-Bit version, while remaining the zoomed out camera, would make this a lot better to play as you pass the ball around.
3. Yu-Gi-Oh! Dark Duel Stories (GBC) & Yu-Gi-Oh! Forbidden Memories (PS1): I'd say both of these have an issue that plagues most of the franchise, and that is if you're going for 100% completion, or simply going after a few cards... the drop rates are a pain, sometimes 1/2048... add a store where you can buy specific cards for some currency.
Well, those are just some changes I'd make. I know many would too, for tons of other video games, so voice them here, anons!