Best possible "glide ratio" (if you want to call it that) for a Robinson R44 in an autorotation is about 4.7:1...or what I saw online comes to 1 mile for every 1300 feet of altitude. That's actually pretty good and I'm used to quite a bit less for most helicopters, but you'll get at least 2:1 if you're within the proper parameters (e.g. rotor RPM and forward airspeed).
The biggest difference to me is that in a helicopter, you will (should?) be touching down at or near zero groundspeed, while in most airplanes, you'll be touching down generally in the 50-70 knot range.