My favourites are exploration games with a lot of unexplored areas.
My favourite games frequently include exploration and the discovery of strange objects, even if they are not physically present.
Research is necessary for many of my favourite games since it reveals intriguing new features.
It's the exploration of new aspects beyond the physical that usually makes a game intriguing to me.
Games with a lot of hidden features and mysteries appeal greatly to me.
For the most part, I like games that encourage exploration via a plethora of secret areas and surprises.