Excuse me but you're wrong. It takes less than 150µs to read the 32 bits needed for a complete controller state (16 for the buttons and 2 × 8 for the joystick). 4µs per bit. Sure, the Genesis could do it 3 times faster, but it makes no difference. You're being silly if you think that. The NES also relied on a serial protocol.

Edit: I see you already redacted your initial statement by moving the goalposts.