Is it best to keep analog and digital lines on seperate cables?

I'm working on a console style Naomi system and some games, namely World Series Baseball, need analog inputs. Well, as you know all buttons and normal joysticks are digital...

My digital system's instructor has told us to keep analog and digital lines and parts as far apart as possible as to no introduce noise from the digital signals into the analog signals.

Is is nessicary for me to run two seperate db15 cables from the control panel to the system, one for analog and one for digital? Or, could I just use one large db25 and run them through the same bundle of wires?

Also, does the gauge of wire hamper analog signal?

The gauge of wire won't matter, as long as it's not REALLY, REALLY, REALLY shitty wire. And yes, you might want to use two bundles of cables. In addition to shielding the wires from each other, it also makes it easier to disgnose/fix problems with the wiring.

I'm planning on using a vga cable for the analog signal and neogeo extention cables for the digital, then I'm going to use spiral wrap to bundle them together.

What do you think would be the best distance to space the surface mount connectors from each other (in the joystick casing and system casing)? A couple inches?