We go to Myrtle Beach once a year. I give Myrtle Beach a 4 because it is not one of the prettiest beaches I've ever visited, but it is a lot of fun. Myrtle Beach is a tourist destination. I have heard people say they don't like Myrtle Beach because of that, but it is exactly why we like it so much. You have the beach, plus more.
There are fun miniature golf courses everywhere, all with different themes. My son loves picking one out and we have fun playing. We enjoy going to the beach during the day and eating out and shopping at night. We love going to Broadway at the Beach for shopping. There are tons of seafood restaurants. Most are "all you can eat", which my husband always insists that we do one of these during our stay. We usually end up at Crabby Mike's or Benjamins.
There are also several water parks in Myrtle Beach, which is a lot of fun for the kids. The trip can get quite expensive if you decide to do a lot of activities. If you don't want to spend a lot, you can have just as much fun just hanging out at the beach and hitting some shopping areas to just browse. The piers usually have activities going on at night with some local bands.