Updated December 7, 2020: New entries added
Action games top the Subcategories section of the Google Play Store.
Admittedly, that's due to alphabetical reasons, but it could just as well be because of its primacy on the wider smartphone gaming scene. Action games are everything.
Think about what sort of genres fall under the wider action umbrella: first person shooters, side-scrolling beat-'em-ups, platform-shooters, rogue-like hack-and-slashers, twin-stick shooters... the list goes on.
There are no hard and fast rules that define an action game. Just an onus on kinetic aggression. We hesitate to say 'violence', because some of the games on the following list don't land a virtual blow.
Basically, you fire up an action game when you want to let rip. To blow off some steam on some digital targets.
The best Action games guarantee a good time in short bursts. We could all do with a bit of that right now.