Ever since I was a little kid, I have been highly trained in the art and science of receiving presents. My sister and I would get the same lecture from our parents every year when we were driving to our birthday parties: «No matter what you get, whether you like it, hate it, or already have it, you act like it’s the greatest thing you’ve ever received and you say thank you to the person who gave it to you.» It doesn’t matter if you’re 4 or 94; that’s excellent advice. Nobody who took the time to shop for and buy you a present should feel like their time and effort was wasted, even if it was objectively not that great of a gift. 

If the gift in question is exceptional, that’s all the more reason to wrap your arms around the gifter and thank them profusely for their generosity.