the designation "C" RPG was literally instituted after the release of BG2 to differentiate it from the gold box and "J" RPG coming across consoles from Japan.
BG2 literally established the CRPG genre, and it's fundamentals were carried forward in practically EVERY story based RPG that followed it.
Google says it was first coined in the 70s, but i won't argue because i don't know that much about gaming history.
Bioware's RTwP system is the precursor to the weapon wheel, which is one of the MOST immersive additions to action RPG and FPS games in history. They evolved their RTwP system for DA:O and Mass Effect.
Sounds somewhat far fetched, but again won't argue since i'm not an historian. And this game doesn't use RtwP.
In my opinion, NONE of Larian's products has ever had this kind of impact.
And none of modern FPS have the impact of DOOM. DOOM did it by being "first" widely played FPS. It refined the formula and launched a genre.