I would much rather receive a GG if the game was good, or bad, or down right ugly on my end or the other guy's end. Getting no GG(sometimes though it happens because you typed it too slow and game ended) because it seemed unbalanced to me is, well, worse.
Just common courtesy to offer a GG. if the other person really feels it was not, he will type it out. This I know, I have seen it. I have to go with Frey on this one.