@Ironman
One, the PC is not a MS platform. MS simply provides the OS, others provide the GPU (Nvidia, ATI), etc. You cannot declare it is an MS platform. It is a general computing platform requiring multiple parties.
Two, few PC titles can be claimed to be MS titles on PC. For that they would need, I would argue, to be published by MS or use GFWL. For example when I buy L4D2 direct from Valve via Steam all money goes to Valve. I use Valve's services to play it. The OS is essentially as irrelevant to this as the video card - needed, but not having ownership of the title.
You're trying to twist MS's fairly small, and regarded by majority of PC gamers increasingly irrelevant position regarding gaming on PCs, into something major, and you're wrong in that I'm afraid.
The PC isn't a MS platform, it isn't anybodies platform exclusively (you were almost arguing that well but tripped yourself up by then overstating MS position). MS simply has a 'virtual' monopoly on one element of a PC, but there is still the motherboard, the GPU, the HDD, etc. etc. You can't suddenly decide the OS vs the HW components determine the platform.
Three, 360/PC or PS3/PC titles are not full exclusives. They are most similar to 'timed exclusives'. Why?
A full exclusive would require you to have one specific platform (specific to gaming like a console, or general purpose but capable of gaming like a PC) to play it on. Halo 3 is a full exclusive at this point, as is Gears 2. You want those, you MUST have a 360. Uncharted and Killzone 2 are full exclusives, you want those, you MUST have a PS3. World of Warcraft is a PC full exclusive - you want it, you MUST have a PC (or hit the internet cafes with a lot of cash).
Sorry, but I'm not interested in folk deciding they can determine a word's usage. Exclusive means single, sole. I do accept we need, by necessaity, to consider special cases due to the nature of titles being 360/PC or PS3/PC, but those special cases by definition are clearly not going to satisfy the conditions of being a true and proper exclusive.
Mass Effect, Bioshock and the like are similar to timed exclusives - they deny access via some platforms but do not lock you down to one, exclusive platform. Also, I'd note that, increasingly such titles really are timed exclusives. Bioshock on PS3, Fallout 3 DLC hitting PS3, etc. When something has an expiry date when its conditions can change it cannot be declared anything other than 'temporary'.
I don't have 360 because the majority of titles I'd want on the system are on PC, and I have a PC capable of letting me enjoy those titles in a manner I find preferable. Therefore it's pretty obvious those titles do not fulfill the main criteria of a full, proper exclusive - I must have the single, sole, one and only platform they are available on to be able to play them.
But I don't, I have a choice, I can chose one platform (general purpose including gaming) over another (gaming specific - sorta - platform) - and therefore they are not full and proper exclusives.
And please, give it a rest with MS platform nonsense. I might has well look at the nVidia tech in consoles and PCs and declare them nVidia platforms.
Consider that Valve, a relatively small company comapred to MS, has a more influential position than MS for PC gaming, has a much strong presence as a service provider than MS for PC gaming, look at the position of MMO's like WoW, etc. and you can see how relatively small MS place in PC gaming is.