I find my brain extremely happy when a game provides ample opportunity to make connections, like in Dwarf Fortress, where I watch an event unfold, which can stir my creativity and imagination like nothing else. Writing a story out of it is extremely smooth and easy compared to other sandbox games.
I also find myself in love with immersive sims like Desu Ex and Thief, where level design and exploration take a front seat, every map is like a big playground with verticality and branching paths, where you find secrets and lore hidden around every corner in an atmospheric world.
What is immersion to you?
A good story with solid world building.
DA Origins. ME trilogy. Dishonored 1 & 2. D&D games always have some of that with complex character building to make up the difference when the story is less than stellar.
Like fun fiction, only you participate instead of reading.