The Minecraft mod Biomes O’ Plenty does one thing. It adds 60 (at the moment) more terrain regions the player can wander through. This is a great example of something simple done very well. The mod isn’t overpowering players, it does not give them an edge in playing the game… But it does make the Minecraft world a lot more interesting to explore.
There is a greater lesson in simplicity for game developers. Simplicity is key. You want the core mechanics and core game play to be as succinct as possible. Sometimes you have to strip out all those bells and whistles that you think might be fun in order to reduce complexity and provide a simple yet moving experience. Biomes O’ Plenty is a simple and great mod. If you have a game idea that’s too big to tackle on your own, can you instead mod an existing game?
BOP (not Birds of Paradise) a great mod, and you should check it out. Especially if you are an Explorer at heart. As of my writing the current version is a bit buggy and causes lag spikes and block lag. The author of the mod TDWP_FTW indicated this has presumably been cleared up for the next release. Looking forward to it!