In Skyrim on Master difficulty, game can be a bit challenging at first wrt knowing which fights to pick (experience with the game helps). The most enjoyable gameplay while still throwing me a challenge is around lvl 20-40'ish. If I reach lvl40 (I don't powerplay, so it'll take a while) I feel the character has become overpowered, the game has become boring, and I restart with a fresh one.