I wanted to say that I developed Rocket Renegade [1] for iOS. It's an 80s-inspired arcade shooter, with elements reminiscent of Space Invaders, Asteroids, Galaga... and, of course, it contains bosses.
I wrote all of the code, and I composed the soundtrack as well. The bitmap graphics were done by game designer Daniel Cook, who released them under a Creative Commons Attribution license.
I believe that it fits all of your requirements: the quality is high, the gameplay is fun, it runs rock-solid at 60 frames per second, the music is awesome, and it's a POP game (Pay Once to Play); no IAP, no ads.
It's essentially a straight-up, gun-for-your-highest-score-classic-arcade-shooter.
[1] https://itunes.apple.com/us/app/rocket-renegade/id955229059?...