Good Timeline scenarios
Gen II
>Good level distribution
>No dropped baby Pokémon
>No dropped beta mons
>Color variations for all mons
>Kanto more fleshed out with quests
>Safari zone
>Celebi post-game is built in and not an event
Gen III
>Can trade with Gen II
>No IVs
>Day and Night
>Proper multiframe animations for mons, no distortions
>No dropped features from previous generations starts here
Gen IV
>Arceus is not a thing
>GB Sounds available at the start of HGSS
>Third entry in Colosseum series exists, Orre is acknowledged by GF. Each new Gen from here on out has a new Colosseum game.
Gen V
>Difficulty settings available at the start
>Battle animations are properly drawn instead of the puppet system
>Older mons get buffs across the board; higher stats, new moves, etc. GF has hired a team that aggressively analyzes the west/east competitive communities and implements changes accordingly
Gen VI
>Colors with more saturation
>Better and more fitting animations in battle
>Tiered wonder trade
>No Megas, just alternate forms or split evolutions
>Evolutions for mons that need it
>No HMs, just TMs. Pokémon have innate HM skills according to their type/species/anatomy/movepool
>ORAS has Battle Frontier
>Can catch AZs Floette in post game
>Most pokemon can vary in size, not just Pumpkaboo/Gourgeist
>Event legendaries and mythicals are quests downloaded as free DLC
Gen VII
>SM2 instead of USUM, which is $10 DLC for SM
>Platinum remake
>Can catch Mew under truck in VC games
>Dex not dropped
>Item/training for switching between all abilities of a mon