I've not been in that industry but was for a while, the closest input metric I ever saw that correlated to success was how fast your tools let you iterate on ideas to find the core of what was "fun" and the polish it until it shined. Same applied to the art side of the pipeline, the more headache importing/iterating in-engine the more things diverged from render -> in-game.
Oh and how much publishers meddled in games and/or set constraints. At one point one of the big 3 wasn't approving games that didn't have multiplayer regardless of genre, got to spend ~5mo working on multiplayer that was totally broken until we got sign-off that we could pull it from the title.