gg, as it were, should signify more than a simple salutation offered when admitting a losing effort.  It should not be offered unless all members of a team aggree to call it, number one, and two, it also should be returned out of respect by the winning players.  At least this is how it has come to be known.

I think it's a gg when the outcome hasn't been decided after 1 hour where the balance of power could still tip either way.

GG is when i can fry someoen with kosturas or when someone is trying to fry me

GG is the white flag. But a truly GG for me is one in which I have a challenging opponent whose skill matches my own, and win or lose is decided on cunning and strategy. I had a gg againsta guy a few days ago that lasted only about 15 minutes. Our HWs were connected so naturally, we engaged very early. After what seemed like a really long battle, I came out on top, but I wouldve considered it a GG had he turned the tide on me and came out the winner because it was that close. I also consider GG when I learn something valuable from my opponent that I can use. I think generally though its those games where everyone is playing their best, teams are evenly matched, and the outcome could go eitherway. Those games tend to be the longest, and win or lose are definitely the most fun.

I love those games too.  Even when you lose, the game still puts a smile on your face.  Because your team did well together, you "almost had them", and some awesome battles took place.

You know, the games that you can't tell who is winning, AND THEN your fears start to become reality, AND THEN your team catches a break like with a decisive win on one side of the map that ultimately turns the tide...AND THEN especially if it was your contribution through micro-ing, or tactical excellence that made the difference...snatching victory from the jaws of defeat...AND THEN all the while the opponents team had some guy on their side smack talking the whole time...AND THEN he just sort of has to shut up...

Those are the best "gg's".

A good game is something unqiue, something thrilling, something that's a cut above the average game.  Preferably it concludes in a spectacular and climatic manner.  Games like those are worth savouring.

I know a Capture-the-Flag server where, if the score ended up being 5-0 or 5-1, when you go to type "gg" it comes out reading "bad game".

Jep.  It's supposed to be a noobies friendly type of server.

A gg is whenever I beat my opponent with massed flak. But seriously, a real good game is exactly what Darvin described; one that is unique and climatic. One particular example I can think of was a match last patch, where one of my enemies (One of Siddy's smurfs, I think), built 7 Halcyons and a Rapture and ended with us in a huge SC battle involving hundreds of Bombers.

And preferably involves enormous amounts of flak.

Well, that depends on how you wanna define "GG."  I have 3 takes on it:

TAKE 1: "GG" signifying the game was well and truly an epic fight, and whether or not you lost, it was a good time nonetheless.

TAKE 2: "GG" signifying an event that, should it come to pass, pretty much means the other side pretty much has no choice but to wave the white flag of humility.

TAKE 3: "GG" signifying the common phrase used when the game's over.

For take 1, a lot of Castle Fight games I've played on Warcraft III: Frozen Throne have been like that.  Castle Fight is a custom map in which you have a single, invincible worker to build unit-producing factories with.  They can also build defenses or "Legendary" structures, as well, which use a piece of wood to construct (and a piece of wood costs 1500 gold to get 'em at your castle (the only way to get another piece), so they're not cheap).  The goal is to simply overwhelm the other team and destroy their castle.  There's a bunch of other details, but to get to the point, a game could last 5 minutes, or 2 hours, depending on how experienced you and your teammates are.  And then there's some games that just reach a stalemate, and players can agree to call it a draw.  The games I enjoy the most are the ones which both teams fight well, and whether or not I lose, it was still a great time.

For take 2, I have a technique that I like to use in Sins (should I ever get to said stage) with the TEC called the "Fan of Death."  Basically, it involves putting a Novalith at every world I own in a star cluster (ideally, one that's well-protected), and then launching every single one at enemy planets.  Since I hotkey my "Novalith Network," it allows me to quickly fire a volley of nuclear destruction at my hapless victims.  Granted, since I've never played online, how well this would work is disputable, but it's fun to do, nonetheless.

Take 3 I don't think needs much more be said. =P

I think GG it's a game with lots of turnarounds in it. A lot of changes who is on top and where you counter your opponent then he counters you.... In that games Power is like pendulum it swings from one team to other and back.

Lately GG means one team was defeated or won.

And after some games I ask myself what was good that everybody is saying GG when one team was owned in 20 or 30 min. 

LOL yeah your right RabidRabibit.

But wouldn't it be better if there actually was a game.....