'everything' has been done before.
don't worry about a game being 'cliche'
every storyline starts with a cliche. The idea of good vs evil is a damn cliche already. It's the detail, development, and plot that makes the game original.
take a base storyline, even if its a cliche goal, there's the base. now with interesting characters, events, twists, and events, you can flesh it out and make an original game instead of just that worn out cliche.