If a game is too similar to the previous game then what would the point of playing it be? You could just stick to the last game. Original games just bring new ideas and make it more fun. Just imagine listening to one band do one song over and over again till the end of time.
Game consoles are only "cheap" for the end consumer. It cost alot of money for console makers in terms of technology research. Also, console makers sell their consoles at a loss. If you were to pay for every componet of a console then the consoles would be alot more expensive.