I do think there is such thing as a bad bj. To me a good bj involves eye contact, some soft stroking of my cock, and some very wet sucking. Starting slowly and then picking up speed. I think I also like to be standing up, since more often I'll be lying on my back... I guess variety is important for a good experience!
I also have never had a bad blow job.... Now the best blow job started with me standing, after a min or two she could tell i wasn't getting comfortable. She Said sit down baby, so i did, after some long slow loud sucks. she began to lick my balls and jack me off... after a few min she gave my balls a nice tugging and jacking of my dick..... THAT'S WHEN SHE PUT HER TONG IN MY ASS... AND OH MY GOD... I GOT SO HORNY I HAD TO FUCK HER DIRTY ASS... Paid the more money put the rubber on and FUCKED THE HELL OUT OF HER.. To this very day I can still masturbate to that memory...