What are some good games worth buying on play store?

shattered pixel dungeon is a good time. It's FOSS and you can also find it in fdroid.

Adding to a FOSS list: Mindustry and Unciv. The latter is an amazing Civilization 5 clone.
Hey what's the difference between Shattered Pixel Dungeon and Pixel Dungeon ML?
- ML appears to be a fork with improved multi language support

Dead Cells
Dicey Dungeons
Stardew Valley
Bloons TD 6
Slay the Spire
Castlevania SotN
Baba is You
The Room (and its sequels)
Game Dev Tycoon

Friendly reminder Bloons TD 6 is free for Netflix customers. Unsure if that's all counties or restricted or tier restricted. It's been pretty fun, but the best aspect is offline play.
- Oh yeah, there's actually a fair bit of good games on Netflix if you have a subscription. Unfortunately, they're online-only even if they're singleplayer... I hate subscriptions...
  
  Sonic Mania, Shovel Knight Pocket Dungeon, Into the Breach, and Wonderputt are pretty fun. I haven't tried anything else.

Slice and Dice: https://play.google.com/store/apps/details?id=com.com.tann.dice

I've gone back to this game so many times, it's truly a treasure! He gives so much with every update!

Into the Breach is free if you have Netflix. I'm not sure if it's for purchase otherwise but it's a ton of fun.

I've never had so much fun staring at the screen for minutes on end without doing anything. Calculating my next move. Great game, but definitely not one you can just play mindlessly.
I hate that it's a Netflix exclusive. Let me buy this. Surely it's one of the best game out there.

Monument Valley

I HATE playing mobile games but my wife got me hooked on Dawncaster. It's a roguelike deck builder. I think it's like $4-5 and no micro transactions but there are expansion packs to add new zones and enemies. I've since picked them all up. It's regularly updated with free content packs and balance changes. The devs are very responsive with the community.

King of Dragon Pass is ancient but worth picking up on mobile

Night of the full moon is a good card roguelike. They've recently added modes that play like hearthstone and other card games too

Peglin is a good peggle spin off

Solitarica is a solitaire roguelike

Solomons keep/boneyard are fun dungeon crawler roguelikes

Pawnbarian is a chess roguelike

Dead Cells
Titan Quest
Worms WMD

Of all the games I played on Android I think Monument Valley was the only native mobile game that I really enjoyed. I also played Stardew Valley on mobile, that worked quite well.

I've bought Stardew on nearly every platform I've had, and I would happily do it again!

The professor layton ports worked well.

I've got a lot of mileage out of Pocket City 2.

Not gonna lie only game I play on mobile is clash of clans. I don't play mobile often and don't spend money on it either. Been playing since middle school though off and on.

In addition to a few I've seen posted already (Stardew Valley especially)...

A Dark Room: A relatively short, minimalist, mostly-text-based RPG with a dark vibe. I come back to this at least once a year. Can be played free via web browser, but the native app version has some extras.
Dysmantle: A huge and well-polished zombie survival sim. Just recently finished it and was really impressed with the overall scale, level design and progression.
Papers, Please: A 'dystopian document thriller.' You play as a border checkpoint agent, verifying increasingly-complicated passport documents and questioning your moral compass. Port of a PC game by the same name.

https://sh.itjust.works/post/22476834

Redcon You can try it for free, but to finish the campaign you have to buy it