i always wish 'have fun :)' and thats what the game should be about .. and what i really wish for my opponent (and myself) :)

if someone wishes me gl though i respond with u2, if someone wishes me 'good luck' then i respond with 'you too', etc :)

i dont think saying 'gg' or 'good game' or 'well played' at the end of a game when you won it is to rub it in .. its to tell the player who lost that he played a good game even though he lost, the dice might have been against him, even though he played well he still did lose due to some other factor, but that doesnt mean i cant tell him that i thought he played well :)

i often dont say 'gg' or anything in individual games in multigame matches though :)