Here's how it works. Right off of gearsofwar.com
Quote by Epic Games:
Lets take a moment to look over the ranking system in Gears of War 2, to make sure everyone understands what theyre looking at when they check out other players online. Your rank in Gears of War 2 multiplayer is based on your TrueSkill rating, which calculates the relative strength of all players on Xbox LIVE. Gears of War 2 RanksThere are five ranks total, and the first rank is achieved after you play your first multiplayer match. The more Gears 2 matches you win, the higher your rank will be, and your rank will go down when you lose matches. Rank is not affected by Horde Mode and private matches. The ranks are displayed in game using the icons to the left. TrueSkill is like the chess ELO system, which tries to predict who should win the match based on the skill of the players. If you were predicted to lose and your team wins, then your TrueSkill goes up more than if you won and you were predicted to win. This holds true for the inverse scenario: If you were predicted to win and you lose, then your ranking drops more than if you were predicted to lose. Rank is not a constantly increasing value, such as is typical in role-playing games (RPGs). Your rank may plateau or even drop as it closes in on your correct and accurate skill level. It will probably take tens of Public Xbox LIVE matches for your rank to move in one direction or another, and it may even take hundreds of matches to achieve a skill with the highest rank we offer, assuming you are good enough to get there. Also, keep in mind that each rank icon represents a specific range or bucket of TrueSkill values, so while your skill is fluctuating in very small increments from match to match, your rank icon will only change when your skill moves from one bucket to the next. Therefore, your rank is not just about number of kills or experience or the amount of time played. It's an aggregated representation of your skill level based on your wins and losses during Public Xbox LIVE matches. And yes, quitting will lower your rank. - Six Okay
