I was averaging 5:40 or so until a few years ago (back problems). I started running again a few months ago. I'm probably a little over 6 right now, but I've been doing intervals lately so I can't say for sure. Anything under 6 is respectable. Anything under 5 is awesome (never got there), anything under 4 is grounds for a kryptonite sensitivity test.
I usually run 3 miles since that's why my PFT is and I can do that in 21:00 or so, but that doesn't really mean anything cause if I know I'm only running a mile, I"ll run myself harder and possibly knock the time town.
Waayyyy back when I used to run miles for time my best was a 5:07. Now, I have no idea but I'd venture to say it's over 8 minutes. 200+ pound non-runners, don't keep good mile times.
I've found running to be an odd measure of conditioning though as a bit of sport specificity seems to come into play. I've found that you can have good conditioning, but if you don't run, your mile time can be truly poor.