The Games Played count seems to do weird things for co-op games. I just played and completed 4 games on co-op arena crushing and both my friend and I have stat pages that went up by 10 games.
I just completed a game joined in-progress, Desert Village/Hard, and my game count went up by 4.
Ok, I suspect I know what's going on. Played two custom co-op arena matches with one other person.
London Streets - Hard
3 deaths, round 10 completed
games played increased by 4
Oasis - Hard
0 deaths, round 10 completed
games played increased by 1
My working theory is that games played is increased by one for the match you play, and an additional one for every time the team dies and you have to restart a round. I'll see if it also adds one for each individual death where you are able to respawn during a round without the whole team dying and restarting the round.
Update 4/11/2012 8:52pm
Game count goes up by an addition one for every round restart caused by whole team dying. Does not go up if you die and respawn within a round.
Uncharted 3 has too many problems that must to be solved:
1) Friendly Fire (annoying when a teammate kills me)
Forfeit? During the search for players, happens that the server lose players (completely normal) but if I go in lobby I get the defeat (not normal) without ever having played the match!
3) It is not correct! Teammates are placed against, even if they are part of the same clan or just friends. Even if the players found are weak, it is not correct that I must to play against them!
4) Colluders (there are still bugs that need to be closed, many players use them to their advantage)
5) KAL-7 is too powerful (many weapons changes have been made, but the only weapon that needs to be weaken is the KAL-7). There will be a reason for the weak players prefer this weapon: it is the most powerful weapon in the arsenal of all multiplayer of Uncharted 3!
6) Players immortal? Sometimes it happens that after you die, you can not regenerate, and because of this bug you are free to kill the opposing team without any trouble!
7) What? It happens that I was killed, but return to life only to die at the same time under an enemy grenade.
8) Rarely happens that after killing someone, I do not get assigned the kill even though the body of those who I killed is still on the ground!
9) Ejected? The server expel me from the match and I not assigned to the killings and even the victory (not my fault if some members of the opposing team abandoning the match and make the match more balanced the game must to eject the best players, just because the other team is too weak)
10) Match doomed a defeat (playing alone it happens that you get into a match in progress already condemned. I prefer Uncharted 2, where the match in progress not exist!
11) After the players have been found, it happens that I have to wait while my friends make a match (both me and my friends we were in the lobby)
12) Strangely, it happens that unintentionally I enter in a bug and for continue playing are forced to kill me.
13) Sometimes it happens that the kickbacks do not work and some chests of treasure can not be looted!
14) Rarely happens that the match starts to a black screen and for continue playing I turn off the PS3 (lost by forfeit)
15) During the climbing happens that the character moves to the right or left, when I instead had selected the cursor up!
16) When there are too many weapons on the ground, it happens that you can not take the weapon that I want to take but I instead is taken one that I don't need!
17) While viewing the cinema file crashes PS3.
18) In the Mesh Block Map (Lab) regardless if I win or lose the match, the data not added to the my personal statistics, but if the match is abandoned (not to jeopardize the relationship kills) assigned me the defeat! It's not fair!
Thanks for wathing 
