In the English-speaking community, it's relatively clear that classic Sonic fans' influence is the most prominent, not only in the community but in terms of how Sega dictates the direction of the series. In the US and presumably Europe, the overwhelming majority of merchandise is related to classic Sonic. But more obviously, you have-
1) Sonic Lost World, who very clearly attempts to capture the aesthetics of Sonic 1 on the Genesis.
2) The transition from fully-3D to 3D with classic-inspired 2D segments starting with Unleashed was an attempt to make the games more well received like the 2D games, which are praised for being the closest things to the classic titles.
3) Sonic 4.
I love the classics. They're some of my favorite video games ever. But I empathize deeply with those who may be a fan of later incarnations. Or, hell, fans of DIFFERENT incarnations of the series in general, that are put by the wayside because Sega is in a position where they feel the need to bank on nostalgia in order to get any sort of revenue and avoid preemptively shrugging off as too srs 4 sanic.