Originality doesn't have to be an entirely new thing. It can be taking one thing and expressing it in a different way. Look at what Cowboy Bebop did for Western Jazz, and it's widely credited as one of the best animes of it's time. It can be using an abstract artform, it can be using post-modernism, it can be avant garde, it can be an objet d'art, it can be reproducing an old classic with a different art style, it can be changing the setting of something, or it's genre, or tone. A good writer I once had the pleasure of meeting said that too much originality is a plague. You could make a novel based on Jupiter where all the characters are gas based life forms with an entirely new social structure, but that's asking a lot of your readers to buy into. Eventually it becomes more about the reader's attempt to comprehend something and less about the skill in which it is told. I believe this works for all mediums. A clever twist on something, or bringing together two contrasting cultures or genres can generally create originality.
As for games specifically, a lot of the best games of today are based on original ideas that now seem mundane as we are so used to them. I'm sure a lot of more successful games will be surprisingly original.
As for games specifically, a lot of the best games of today are based on original ideas that now seem mundane as we are so used to them. I'm sure a lot of more successful games will be surprisingly original.