I believe a tattoo should have meaning to the beholder, and a great tattoo is one that is loved by the beholder in spite of other's criticism.
Slag tags and tribal sleeves aren't really in this category for me.
I am going to be getting my first tattoo in a few weeks, and it means a lot to me. I have had friends look at the design and sneer at it because they think it is ugly, but it holds a lot of meaning to me and I personally can't wait to have it immortalised on my body. It isn't a picture, just an altered excerpt from one of my favourite books. I will love it forever and have patiently waited years with the design in my head, and will be getting it done temporarily as a trial run to make sure I still love it.
I completely understand that some people consider a tattoo to be a blemish upon the human canvas - I really do. It's just for me, a tattoo should be an extension of one's passion, love, creativity or hobby. No matter how subjectively ugly, if the person who holds it finds it beautiful, then it's right for them.