I think part of what makes any place special is the wonderful memories you may have of a terrific trip.
I personally love Hilton Head for a couple reasons.
The beach is gorgeous and goes on for miles and doesn't get as crowded as some other places.
There are bike paths all over the island so you can ride through all the plantations and such on sun dappled bike paths.
The golf courses are beautiful.
There is a ton of shopping...everything you can want, but it has been developed in a way that you don't even see the shops from the main road. Not as "tacky" I guess people would say as other places.
You can always find a quiet spot away from the crowds.
Lots of activities...kayaking, biking, golf, boat rentals, sailing, parasailing, surfing, etc. Keeps everyone busy.
Fun restaurants so I don't have to cook!
Able to ride bikes along the beach for miles.
Close to Savannah and even Charleston for day trips.
Those are my resons.