Mario Gomez was the main goal contributor to Bayern 2010-2012. Does anyone think he was the best player above Ribery, Robben, Muller, Lahm, Kroos, Neuer? No one.
Does a hard assist, that only KDB could do in the team, have the same impact as an easy assist? Does a goal for 4-0 have the same value as a goal for 1-0? The most important stat is which goals/assists were fundamental to get 3 points. Even then, 2-1 against Dortmund was thanks to an excellent pass by KDB, but that was not an assist, how do we count those? Even then, for Man C only 5 players are really offensive and have the shot to be the one who has the highest amount of important contributed goals. Does that mean that the other 6 players cannot be the most important player for City?
Give me a player that has 20 goals+ assists, but manages the tempo of the team, has a champion mentality, great technique and dribbling ( a Foden or KDB), over a 40 goals+ assist whose only contributions to the game are the goals and assists (Mario Gomez). The only way to know which players are the most important for the team is to watch the games.
I agree that for 2017-2019 Sterling was top 2/top 3 player for Man C , but there is no way he's been the most important player for City in the last 5 years. KDB and Aguero are the most important for the team. Sterling is probably the third.
About this season, let' focus on how the team plays, and which players are fundamental to the way we play. Those, and the ones who have scored important goals or assists or great passes or managed the tempo of the game, are the best players for the team on the current season, not the ones who score the most. I would say that: KDB, Dias, Gundogan, Foden are easily more impactful than Sterling this season. And players like Cancelo, Rodri, Stones, Bernardo have had more impact on the way we play than Sterling. Even Mahrez and Gabriel Jesus have an argument to be more important players this season than Sterling.