I mostly play on-line chess and I always return it, but when I play blitz I hardly look at chat. My guess is some of your opponents don't even see it.
GGGGGG

I find most do respond to "gg" messages, but a number do not. Is it rude? Well, maybe, but I don't let it bother me any.

dont worry about it, same here. i personally used to always start a conversation but now it just seems distracting. a lot of people i used to talk to were mean though, but some were friendly, sharing suggestions. a simple gg back would be nice but if they dont, just carry on.

Yeah, well....some people don't care to respond. Perhaps they are intentionally rude. Perhaps just busy (and inadvertantly lack social graces). Nothing new here. I don't give it much consideration.
Hank

The first time someone said 'gg' to me, I thought they were calling me gay (gg could mean gay guy or something like that). I figured it out pretty quickly, but still, If I ever say something, it is 'Good game.', to avoid ambiguity.

I always say "good game" when I lose... if I win (especially if I win via my opponent blundering really badly) I'm always afraid of it sounding condescending, so I generally wait a bit for my opponent to say it or to leave the chat.


half the time, I dont see the comments. But I try to be courtious at all times, win or loose. I dont respond to badgering or stupid comments, however, I would never feel that a gg or something like that was given in that light. Even if I lost badly due to really stupid moves on my part.
So, if no response to your gg, no worries I would put it down as they did not see it.
no one ever says "gg" back to me when i say it to them after a game. seems a little rude to me. comments? :P