I know mobile games generally have a lot of bad qualities, shovelware, microtransactions, ads, gacha etc. but I still like a few and I and tons of free time at work so I always am on the look out for good ones.
Plants vs Zombies is a really great tower defense(?) game with nice music, a really good difficulty curve and the entire base game can be completed in about an hour or two.
Plague Inc. A very nice 5-10 min time waster with the goal of killing all of humanity with a virus. This is a really nice game to play with a video or podcast in the background. I will admit it is a touch repetitive but thats probably fine for a game you are only meant to play a couple time a day.
Bloons TD a bright and colorful tower defense game where you take monkeys and pop balloons just a very solid and smooth game
and the main reason I kinda wanted to start this thread
Balatro is a poker-themed roguelike deck-building game and it kinda has me hooked and because its a paid app there are no ads, no in app purchases just a solid game that has made me forget time a few times