A great game I've had on my phone for years is Alto's Odyssey. It's an endless runner, but I found it way better than any other one, because it doesn't get progressively more difficult/unplayable as you play.
Also, if you're into rhythm games, I'd recommend osu!lazer. It's currently in beta and due to Apple's limited beta signup system, you currently can't join, but
here's the TestFlight link if you're interested (they reset it every couple of months, so it's worth keeping an eye on) (also note, that you can just install it on any other platform without any limits, and if you're playing on PC and care about ranking, you should install the
old/stable client instead).
