well actually your monitor cannot display anything above it's max refresh rate (for most monitors 60hz, higher end 120hz, 144hz+). So massive frame rates are really just a novelty, and are only sometimes useful in games that rely on frames such as clonehero.
when you have a frame rate higher then the refresh rate of the monitor then the monitor displayed the most recent image. instead of what ever image it produced anywhere in the 60th of a second that the gpu has to make an image. it may not make sense but you can feel it