I really, really love you and you're awesome in every way. Except one...
You give really bad gifts 
I'm so sorry, but it's true.
On my husband's birthday, you gave him the same cologne that Grandpa uses. The one that includes "real human pheromones." That's kind of gross, and I don't want my husband to smell like Grandpa anyway. Not that I don't love Grandpa, but that's just strange... Now you've given the same cologne to my FIL for Christmas. Again, gross...
We also strongly suspect that the perfume you gave my MIL for Christmas is the same one you use... Can't we all smell differently?
On our ski trip, you sent me off with
eight Ed Hardy hats for the gang... I'm sorry, but they are hideous. Ed Hardy's hats are ugly. I feel so badly about the fact that you paid for them, because I know they aren't cheap
You've also given my husband the same watch for Christmas two or three years in a row. And you gave that watch to my best guy friend as well. Now he and my husband have four of the watches between the two of them...
I won't even start on the strange things you've given me...
But I'll never actually tell you this because you're amazing and so generous and I would never want to hurt your feelings.
Everyone knows it's the thought that counts, and we all love you very much 
Merry Christmas!