1A current in a standard 10 gauge wire has a drift velocity of 23m/s, the wave propagation is dependant on quite a few other factors. The SNES controller is on a 20mA loop, with short to ground IIRC and the wire is likely to be 18 or 20 gauge, the velocity is still not nearly as high as you think, since the loop is interrupted you also have a delay on the sense line. Overall a 30ft cable adds about 2-3ms of latency to the controller...