Personally, I have no intrest in the Wii, but that is just my opinion, the motion controlls just don't appeal to me. However, I'm not sure whether it is worth it if you already have a 360, cause only a small amount of the time that you spend gaming will actually be exclusive, and the main disadvantage of a Wii is that it lacks the major multi-platform games, but the 360 has these.

I may as well end up with a Wii this Christmas:

Xbox: Halo

360: AC, Dead Rising, Naruo, Bioshock, Orange Box

PS2: Ratchet and Clank

Wii: SMG, RE4, Super Paper Mario

Because you already have a 360, and for now, only want (can afford, have room for, whatever) one other console, I can't see really a strong gaming reason that you could favor a PS3 over the Wii.

Now, non-gaming reasons are plenty. For BlueRay, linking up to the network to help 'create' super computers, etc. Others could tell you that drill much better than I. And of course, not finding a Wii is incentive for not buying it as well. ;)

But for a different experience of gaming, assuming you want that, you have to go with the Wii.

Oh, and you didn't mention what you will be watching it on. For example, if your 360 hooks up to your big HD TV, but the second console will be in another room hooked up to an older 28 inch TV, PS3 won't be able to show off its graphics as well.

Lastly, don't lock yourself into a mind set. If you want to, I'm sure that you could sell your 360 and buy a PS3 instead. Not that I recommend doing that, but any PS3ers out there think he should?

Do you have a DS? If no, have you considered getting one?

I had a DS. It was stolen about a year ago.

I'm not saying anything bad about any of those games, but:

FFXIII: Early 2009 if you're lucky, probably more like mid 2009.
White Knight Story (assuming that's what WKS is): 2009 at the earlieist
GoW3: Hasn't even been officially announced yet (not Jaffe running his mouth but official press releasE), no earlier than mid 2009.

Again, don't buy a console for games that are coming out more than a year from now.

 thats all the PS3 has that interests you?

 how about Unreal Tournament 3? Pain? High Velocity Bowling?  Folklore? Motorstorm? Eye of Judgment? The Orange Box?

That was PS2, ssj. I was referring to the original Ratchet and Clank (I have 2 and 3, and always wanted the first one).

Unless you're heavy into multimedia or family stuff, it depends 100% on the exclusive games you wanna play.
I true though that there's a bigger overlap between 360 / PS3 than between 360 / Wii, so that might be an argument pro Wii.

Good luck finding a Wii