One of the most important games ever made, which is Vampire: The Masquerade, was simply based upon the rule of inversion: what if this time, we make a game not about guys hunting monsters, but about being these monsters instead? Take some universal concept, like symmetry and try to apply it to various themes. Modern physics is full of such concepts, read some popular science on cosmology.
Eventually, though, it all boils down to what will you make with it. Gaming genres are pretty much defined, do not waste your energy trying to revolutionize the way to play the game, unless you are going for some new tech, like VR.
Digital gaming is an interactive audio-visual medium, which means, it must involve three impressive enough components: it must make enough sense with being interactive, it must have impressive soundscape and soundtrack, as well as it must feature impressive visual art, not to be mistaken with impressively advanced graphics, though, which is another story.
I would say all digital games further divide between two categories: they are either adventures or puzzles. Adventures need to tell a story. Puzzles, do not tell a story. Adventures can be more linear and naive in a way of structure, puzzles need to be sophisticated in turn.