The Third Party Support
As of the rounds one and two we already found out that the PlayStation 3 has an edge over the Xbox 360 hardwarewise, and that it also has a better catalouge of exclusives, but what about the third party support?
For those of you who are a bit confused right now, ler me help you: As a third party you describe a software developer or publisher that has no direct relations to the console manufactor. EA, Activision, Sega, Take Two and Lucas Arts are only a few of them, and although they create multiplatform titles, most of them don't give equal love to all the consoles. Some of them use one platform as a lead platform for programming, while others may offer exclusive downloadable content. There are also third party exclusives, but those were put aside in round 2. Well then, let's get started.
Lead Platforming
There are only few developers who programm a game on both systems at the same time, notably Infinity Ward, creators of Call of Duty 1 2 and 4, the rest chooses one console to finish the game on and after that ports it onto the other. The problem with that is a substential loss of quality, mainly graphicly, but on the lead platform there are also less glitches present.
The Xbox 360 is choosen as the lead platform in 90% of the cases, mainly because it is much easier to make games on it, in other words most games look and play better on Microsoft's console. Some examples are Fallout 3, Call of Duty World at War, Rainbox Six Vegas, Assassin's Creed, Grand Theft Auto IV, the Need for Speed games and Resident Evil 5. Especially Fallout 3 and Call of Duty 3 are very glitchy on the PlayStation 3, and they also suffered a lot graphicly.
On the PS3 there is only a small list of titles programmed with the system in mind, notably Burnout Paradise, Final Fantasy XIII, which will have 3 discs int he 360 version and only 1 on PS3, and the upcoming Crysis 2. BioShock has higher resolution textures on the BluRay, while Unreal Tournament 3 was developed on the PS3 first. The good thing is, that the graphical differences between games are getting smaller and smaller with every release, and most new games already look equaly.
Exclusive Downloadable Content
To differenciate: There are two kinds of DLC, which are full exclusives and timed exclusives. The latter is only exclusive for a certain amount of time, while the former stays on that console forever.
In this category the Xbox 360 has the upper hand once again. Due to the larger userbase of Xbox Live (more on that in ROUND 4) the developers and publishers tend to release their DLC either exclusive or timed exclusive on the Xbox 360. Examples of that are the Fallout 3 DLC, which featured 5 pieces of downloadable content exclusive to Xbox Live fot one year, the upcoming Modern Warfare 2 mappacks, which will be on XBL one month earlier, The Elder Scrolls 4 Oblivion expansion Shivering Isles, the exclusive two mappacks for Rainbow Six Vegas and las but certainly not least the two GTA-IV mini episodes The Lost and Damned and The Ballard of Gay Tony, both of which exclusively on Xbox Live.
While Microsoft secures most of the content, Sony has some DLC up their sleves,too. Most recently the Joker Challenges, which are only available for the the PlayStation 3 version of Batman Arkham Asylum. The titan pack for Unreal Tournament 3 is also available exclusively to the PS3, aswell as the challenge rooms for BioShock.
Third Party Exclusives
I already listed most of them in ROUND 2 of the comparison, so you can look them up if you want to. The fact is, that the Xbox 360 has not really much more to offer than the PlayStation 3. But some developers like Valve strictly refuse to do games on Sony's system, because they are not able to do it right and do not want to release a half finished product, which won't satisfy the customers at the end of the day. Major third party exclusives on the 360 are Left 4 Dead one and two, Call of Duty 2, Splinter Cell Conviction, Mass Effect and the Command & Conquer francise.
But just because the 360 has lots of them doesn't mean the PS3 has an emty list, far from it! Big name titles include Valkyria Chronicles, Final Fantasy XIV, Agent (the upcoming top secret game from Rockstar North, creators of GTA), Final Fantasy Versus XIII and of course: Metal Gear Solid 4 Guns of the Patriots.
The end result here is a tie.
THE WINNER IN THIS CATEGORY

The first win of Microsoft's console in our little showdown, and what a dominating one! If you are a gamer that cares more about the Call of Dutys and Assassin's Creeds than about the Halos and Uncharteds, and that wants to have everything at first, this is your console.
STAY TUNED FOR ROUND 4, THE ONLINE SERVICES