Kipa (Tesco) are going to build a new store in Fethiye. Sorry don't know when, but i'm trying to find out....(info is from an official source in Fethiye - not just a rumour)
It's going to be just up from the new Otogar (where the fruit and veg wholesale area is)
I haven't been to one yet (closest is the relatively new one at Marmaris) but it's supposed to be cheaper than migros etc.