It's mostly a challenge to stay focused on a mundane task.
The game looks nice, definitely; but the gameplay isn't super interesting.
The trick to the game is learning to jump slightly sooner than you think is necessary, because if you jump before the flame hits you, it's already too late.
Then… all there's left is repetition, as long as you are able to. The pace doesn't change, there are no new mechanics, the music doesn't change, the backgrounds don't change, etc.
If you remember to press the spacebar at set intervals, you can keep it up for as long as you wish.
Around 750 points, you realize that's all you're going to see in the game, and around 1500, I mostly decided to give up. If I made it to 5000 to get the final achievement, I would have probably quit immediately after.
Most of all, the game is missing variety, something new thrown in the mix every now and then to keep you on your toes.
Also kudos to you for adding medals and high scores, and crediting everyone whose assets you used.