Also, bigger, "fatter" pixel sensors of course make a big difference. All the resolution in the world isn't as important as good color fidelity and contrast. It's also why a typical digital back looks more vivid, resolution aside. People will notice poor color, blown highlights, and artifacts far more than whether it's 12 or 20mp.
The Fuji cameras with their expanded dynamic range(dual sensor models), btw, appear to take excellent black and white photos.