The Pathless. Monster's Expedition was also great, but it's not available any more. And that exposed a nasty detail of Arcade: Once a game isn't “available” any more, all of your copies instantaneously stop working.
I started playing Hitman GO again on mobile. Really enjoying that.
Unlike PC and console gaming, mobile gaming's market is practically "Everyone". So there probably are some great mobile games out there, just buried in the charts under what the masses preferred. What's most popular on mobile is going to be a reflection of a very different demographic's interests. Kind of like trying to find the "best" movie from box office charts, you will get a list of the most popular movied, not the best.
The most popular movie today is not ten years old. They have made movies since The Avengers. (Notably, Avengers: Endgame, but less facetiously, a Super Mario movie and James Cameron's Avatar sequel were pretty popular.) I'm not asking for something inventive and genre-defying, just a game that is not literally ten years old.