Gold/Silver gave us split Sp. Attack/Defense, genders, the breeding system, and two new types.
Ruby/Sapphire gave us Abilities, EVs, and natures.
Diamond/Pearl gave us the Physical/Special split.
X/Y gave us another new type and mega-evolutions.
Black/White gave us..... ???
...... what did B/W even do to stand out other than being cemented as the most forgettable generation?
triple battles and rotation battles, formats that literally no one plays, and seasons
and no, it didnt had a good story, the evil team using legendaries and battling N and ghetsis at the end instead of fighting alder is not a good story at all, that shit has been done since R/S/E
Gen 5 was the last time they made a game with long time fans in mind. It was supposed to be a huge throwback to the fresh adventure of Gen 1 where you didn't know anything about the Pokemon you might find, and did exactly what it set out to do.
Having played every Pokemon game since Red and Blue, BW1 are my favorite hands down.
The "Physical/Special split" is actually an inaccurate fan expression. What Game Freak did was change the categories of moves from type-based to move-based.
Moves have always been physical or special. The difference is that, in the Game Boy games, the types defined the category. The DS games overhauled this to make categories apply to moves themselves regardless of type.
This also created the category of status moves, which didn't exist before.
Pokémon XD: Gale of Darkness was actually the first game to do this but Genius Sonority limited it to Shadow-type moves. Game Freak then thought it was a good idea and applied it to the other types.
black and white introduced the power creep that came with the new min/maxed pokes like ferrothorn and the genies. that's a pretty big thing for the meta.
plus, team preview and (especially) weather-setting HAs also shook up the game.