I'll play.

Campaign/story: 

-Uncharted's campaign was epic and sprawling but, in my opinion, the least focussed of the three Uncharted games.  I (and many others) felt that the characters, enemies, and story was far superior in Uncharted 2.  There were a TON of environments in Uncharted and all of them seem fleshed out and alive.  There were some truly spectacular set pieces, too.  There just wasn't a sense of satisfaction, for me.  It never seemed like the world was in trouble, that the bad guys were really that bad (is there a reason they didn't kill Drake instead of.....messing with his mind?).  The final face off wasn't anything memorable.  A great game but not Uncharted's finest hour.

-Gears of War 3's story was the end result of a trilogy of games.  In Gears 1, we saw some glowing Wretches.  In Gears 2, we saw a full on battle between the Lambent and the Locust.  In Gears 3, we finally saw what the heck was going on and got a little commentary on the world's dependancy on oil.  I thought that was nice.  Anyway, secrets were revealed.  People that should have lived wound up dead.  People we thought were dead came back to life (and maybe died).  Stakes were higher than ever.  The characters didn't have the personality or likeability of Uncharted 3, that's for sure.  Yeah, there were a few moments that made you REALLY feel for Marcus, Dom, and Cole but this was accomplished through a few cheap tricks that played at our emotions (even though, a couple of them managed to work).

Winner: Gears of War 3.  While Uncharted's campaign felt like "just another day in the life" for Nathan Drake, Gears of War 3's campaign felt like the stakes had never been higher.  I don't see myself experiencing the same emotions I felt the first time I went through Uncharted 3 if I play it again.  I already know how Drake will escape his "How does he get out of this one!?" moments.  I already know who dies and who lives.  With Gears, the revelations and such seem to be a lot more permanent and impactful.  They changed the games universe while Uncharted returned to the status quo.  In Gears, we lost the lives of people we've known for years.  In Uncharted 3, we lost a ring.

Graphics and Presentation:

There were some parts of Gears 3 that really blew me away.  The world seemed more live in than ever and the battlefields seemed natural and less "set up" than ever before.  The lighting in certain parts of this game are second to none.....but when Uncharted 3 is at its best, it's untouchable.  The sand effects in the desert (especially that last little bit), the water effects in the fountains, the crinkle in Drake's shirt as he walked--Gears took everything from the earlier games and polished them to perfection.  Uncharted took everything from the earlier games and kicked it to the next level.  Both games will impress you--Gears with its towering monsters, massive explosions, and huge environments--Uncharted with its realistic skin textures, environmental effects, and collapsing environments (don't invite Drake to your house--Your floor will collapse if YOU'RE LUCKY.  If you're not lucky, your entire house will cave in!).

Winner:  In my experience, only two games look better than Gears of War 3.....and one of those games is Uncharted 3.

Co-op/multiplayer:  With two-player split screen, a four-player co-op campaign (where people you've never met before are fighting to save you when you're down), a co-op arcade campaign with (game modifications), Beast Mode, Horde Mode, and many variations of the team deathmatch/capture the flag/etc., there is absolutely NO WAY that Uncharted 3 could compete with Gears online.

Uncharted 3's split screen doesn't even take up the whole screen.  It features some dynamic maps (ie: riding a train while fighting another team or trying to get onto a plane) but in the end, it feels like they're relying more on these gimmicks than the gameplay to get them by.  To be honest, I wasn't to impressed with Uncharted's online.

Winner:  Maybe I'm not the best person to guage the quality of online versus modes.  I'm more of a co-op guy.  With that said, I'd take Gears 3's co-op over U3's co-op any day of the week.  Gears 3's campaign with 4 players is some of the best times I've ever had.  Uncharted's co-op, not so much.  I call 'em like I see 'em and, from what I've played, I'd rather play Gears of War 3.

Gameplay:  In both Uncharted and Gears, you can run, roll to cover, blind fire, hurdle obstacles, throw grenades, melee, etc. In Uncharted 3, you can jump and climb (with a healty bit of game assist to make things more dramatic--which is good), have expanded melee, stealth, etc.

Now, Gears of War seems to have stuck with the tried and true.  Yes, there's a few additions (ie: the Retro Lancer charge) but it seems like Epic worked on making the game faster and more precise.  Yeah, some weapons have recoil like crazy but it's not frustrating to try and control them.  Snapping into cover is more precise.  It rarely happens by accident.  With explosions going on all around me, giant creatures destroying the environment above me and tiny nuisance creatures rushing me, I never felt like I wasn't in control of my survival.  If I died in Gears of War 3, it was definitely because I screwed up.

Uncharted 3 has a bigger move set than Gears of War 3.  Stealth feels better than ever before.  My gripes come from the aiming.  It seems floaty and not very precise.  There was one moment where I was on the rooftops fighting several snipers in the distance.  When the snipers weren't firing, I had a brief moment to zoom in and take them out with my sniper rifle.  It was during this moment that the floaty controls really got on my nerves.  It took too long to get on point. As for the platforming--you were never really in any danger.  You know this.  You know that the pipe that was about to break won't break until you jump off of it.  You know that the floor that crumbles beneath your feet has another, more stable floor beneath it.  Once you know that the stakes aren't high, these moments loose their impact.

Another gripe of mine was the focus on melee in Uncharted 3.  In the past, I'd rush an opponent and knock them out.  If things weren't going well, I'd roll out of the way.  In Uncharted 3, my "roll to safefy" button was now also my, "grab an enemy and try to fight them" button.  Sometimes, I'd be facing a group of snipers AND foot soldiers.  To avoid being sniped, the game tells you to press the circle button to roll.  Imagine how well that works when melee takes priority over rolling?  Not very well.  Too many times, I've been stuck in a fistfight that I couldn't get out of while bad guys shot the hell out of Drake.  Too many times, my death was caused by the controls.  When I know what I want to do and the controls don't let me do it, there is a problem.

Winner:  Now, I HAVE to respect Uncharted and Naughty Dog for adding the new stuff--pulling an enemy's grenade pin (though it happens randomly) and watching them explode, the cinematic melee, the vertical combat--all great additions to the franchise.  But they all lack polish.  Even the formerly polished gunplay seems to be a bit rougher (and I replayed Among Theives just to get ready for U3).  Gears 3 just took everything that they had been doing for years and made it all better.  Did Epic take the safe route while Naughty Dog tried a few new things?  Most definitely.  But this category isn't called "innovation"--it's called "Gameplay".  In the gameplay deparment, Gears 3 does what it does best better than Uncharted 3.  I have to go with Gears of War 3.

Overall Winner: 

Uncharted 3, to me is like a Grand Theft Auto.  It does a LOT of things very well but it isn't the best in many of them.  The puzzles and exploration rival Tomb Raider, but Tomb Raider does it better.  The platforming rivals Prince of Persia (2008--it can't compare to Sands of Time, Warrior Within, Two Thrones, and Forgotten Sands) but Prince of Persia does it better.  The melee rivals Batman, but Batman does it better.  The third person combat rivals Gears of War but Gears does it better.  What Uncharted 3 excels at is presentation.  This game took a mediocre story and made it compelling.  It has characters that people love.  Even the new character, Cutter is instantly more likeable than the new characters in Gears (Jayce, Samantha--though Clayton Carmine was awesome!).  I see myself skipping much of the opening game, trying to get to the set pieces or the gunfights when I decide to play this one again.  The campaign was great and the story was absorbing, the first time through.  I don't see that happening with subsequent playthroughs.

In the realm of third person shooters (which Uncharted 3 is not.  Uncharted 3 is more than just that.),Gears of War reigns supreme.  Gears 3 is the kind of game I will be coming back to, over and over again for years and years.  It packs so much more replayability into its disc than the competition.  The story is streamlined and won't get in the way.  It moves at lightning speed and covers a lot of ground.  When the game is over, a lot of impact has been made.  The entire Gears of War Universe has been changed.

When I talk about Uncharted 3, I'll say something like, "Remember how beautiful the sand looked in the desert?  Remember how awesome that fire in the Chateau was?"  When I talk about Gears 3, I'll say something along the lines of "Remember when ***** died?"  Remember how you felt when Cole *******?" "Remember how awesome that boss fight was?"

If this were a thread asking "Which was the best movie", I'd say Uncharted, hands down.  I can watch the story and the graphics all day.  But when it comes to which "Game" I'd rather play?  Alone or with friends, it's Gears of War 3.

The problem with threads like this is that it is hard for anyone to remain objective. You are pitting the two largest and most celebrated console exclusives out this year against each other. Now I understand that many people have both consoles and have played/own both games (I count myself as one of them), but even for them there is the tendency to favor one system over the other. Therefore, it is difficult for the average person to honestly call one game better than the other. I am no exception. I play on Xbox 360 and I prefer Gears 3 over Uncharted 3. This is not to say I do not have reasons (better multiplayer being the deciding factor for Gears), but it is hard to say that I or anyone else can say one is clearly better.

In this case, I would be more likely to trust an impartial third party ... like a Nintendo only player that happened to have the chance to play both games or even a PC gamer. I am just too suspicious of everyone else.

My honest opinion about both, however, is that it does not matter which game is "better." I think that Gears 3 and Uncharted 3 are average games at best, and are vastly inferior to third party offerings. This is my general argument against console wars as a majority of great games I have encountered have been multiplatform.

In conclusion, I will play Gears 3 again, and I have already traded in Uncharted 3. I can think of plenty of reasons one would prefer Gears, but I will be honest here and say that I tend to play mostly on my Xbox which influences my decision. Not that I would really try to defend either game though ... I don't really understand why either one gets any real attention aside from being big exclusives from 2 of the big 3.