jryden: I agree that the "gg" thing is overdone. In the situation you describe, I usually say "Thanks for the match" or something similar - it highlights that I have won, and "suggests" that perhaps my opponent should resign.
Personally I really dislike "gl" and "gg" - if my opponents can't write out a some real words, I'd rather have silence - though I do make allowances for non-English speakers. And not all games are "gg's": a good game is one which was either close, or had some special interesting feature about it - like dramatic changes in position or fortune - probably less than 50% of games. If one player - and I don't care whether it's me or my opponent - has had two pieces blocked on the bar for a dozen moves, no auoto-pass, and an elapsed week or two against a slow opponent to actually resume "playing", then by no stretch of the imaginagtion could it be called a "gg". Likewise an opponent who strings out a lost game for a dozen unnecessary moves without resigning does not deserve a "gg".
And I like Grenv's tennis match analogy - let's not "shake hands" between individual games in a multi-game match.