XBOX/Microsoft is very smart not to open the franchise yet. They'll get 3 out of the way, maximize sales on it in the XBOX realm, then open it up.
But exclusive games are important to Console manufacturers as it gives us a reason to buy the machine in the first place. They sell XBOX machines first (as well as the attendant online services), then games second.
I bought my XBOX 360 because of GOW and when I get a PS3 it'll be because of God of War III.
You make a good point. If all games were multiplatform, which unfortunately is becoming possible thanks to Kinect and Move, there would be no strong reason to buy either console. The only differences would be aesthetic and price-based. This would bring console prices to a low never before seen (no monopolies= low prices), but would drive out of business all but shovelware companies, due to good companies' inability to compete price-wise.
I reckon though that like mobile devices are being ruled by software, the same will happen with consoles. It really is about the games themselves and soon console makers might have to invest in developing really amazing titles rather than placing most of their hope in the machines.
Stil the other real ace in the hole is online multiplayer experience and the distinct portals one must access like XBOX Live.
In the end, you said it - exclusivity is good for everyone!
Can't see why anyone would hate on either console I love the exclusive agreements it means I get to own both... XBOX 360 for all my friends on XBL, Gears, Halo, COD most multiplat games I purchase for XBOX 360 That is where the majority of my friends are plus multiplats look so much better on the XBOX 360. I don't care if you don't agree but they do... The publishers don't want to invest in more developers, more time, more money into a title it would require to tap into actually using all the power the PS3 inside of it so they get it to be somewhat close to xbox 360 graphics but fail. It is easier to develop for XBOX 360 then port to PS 3 with some tweaks.
I use PS 3 for mainly Single Player titles & exclusives like Heavy Rain, Resistance, Killzone, God of War 3, GT 5. These exclusive not only look awesome they are awesome to play. The PS 3 exclusives utilize the PS 3 ability of cells to produce other functions thus requiring the processor from doing a lot of stuff like color & graphic processes. Besides all that the PS 3 is the best damn blu ray player to get it because it does everything.
So in closing no need to hate just enjoy the games that both these modern marvels are able to produce!!
Just to chime in here, I also own both, and agree*- multiplats *do* look better on the 360, but more importantly, I find Xbox Live to be a superior service, both interface-wise and when it comes to speed & reliability of connections. The XMB, and by association, PSN, just "feel" very isolated to me- there's no immediate sense of community, the way there is with XBL. Between all the above, I just feel that XBL's pricetag vs. PSN's (initial) free status (no longer the case, really, with PSN+) is a case where you get what you pay for- and I certainly wouldn't pay for PSN, "Plus" or otherwise.
That said, I enjoy each console for its own highpoints- I bought my PS3 for God of War 3 and the God of War Collection, and thoroughly enjoyed both, as well as Demon's Souls, Valkyria Chronicles, and Heavy Rain, as well as gems like fl0w, Flower, Fat Princess, and some of the PixelJunk games. I just own a lot more games for the 360 than for the PS3 (somewhere on the order of around 200, combined retail and Arcade, vs. 30 or so combined retail and downloadable).
* Edit: I also meant I agreed on not hating on either console, I just forgot to mention that part. It's almost 4 am on New Year's day, and it's been a... chemical... evening, so you'll have to forgive me. Heh.
Microsoft owned the first gears and i think the second. But they do not own the third gears of war so Epic is free to do what they want. Maybe they want to stay loyal to Microsoft, even though they would be making tons of more money if it went multi-platform.