My favorite way for a core loop to become richer over time is when the loop has a very high skill ceiling the player can move through in a semi-controlled way.

My favorite way for a core loop to become richer over time is when the loop has a very high skill ceiling the player can move through in a semi-controlled way. For multiplayer games, this means good matchmaking, but for other games this is layered in via optional challenges/achievments/bonus goals etc. The stated goal of the game (aka reaching the ending) may or may not be along this path.