Ok, is this closer?

Genesis -> VGA
Red - Pin 1 Red out
Green - Pin 2 Green out
Blue - Pin 3 Blue out
Sync - Pin 13 Horizontal Sync out
Ground - Pin 5 Ground

...or do I also need to ground all the returns?

Also, are the monitor ID pins necessary? Will I still get a picture if I leave them unconnected? My TV has an "RGB-VGA" port, so I'm guessing this is worth a try once I figure out the right pinout.