Broadband speed is a slight misnomer, there is a transfer rate and latency. You can have a broadband that can transfer vast amounts of information but if that information needs to be transmitted to the other side of the world and back, there will be a limit to how fast it is physically possible to do all that. Cloud gaming tends to run on lower graphics settings and resolutions to reduce the sheer quantity of information that needs to be transmitted but the bottle neck on things like real time multiplayer games is how long it takes to send the information from the user to the server and then back again. 20MB/s and 200MB/s will make no difference if the amount of information transmitted doesn't pass 20 but a latency of 10ms vs 100ms will be very noticeable.