Tons of game have used the cel-shaded style though. Crackdown1 and 2 and a Robotech game last gen just to name a few. I have honestly never heard anyone complain about games having similar art styles before. There was some TPS that came out of Japan a few years that looked just like Gears of War and I dont think anyone got upset.
Gearbox offered work for the author of the film and then suddenly dropped him. And used his style anyway.