Although this question is highly subjective, teetering on a flame war, and about two great cameras that aren't really in the same class as each other, if I had zero gear invested, and an unlimited budget I would pick the Nikon D3x. As a Canon guy who owns and loves his 5D Mark II, the Nikon D3x and the 14-24mm f2.8 Nikkor seriously made me consider selling my gear and switching.

Now, the 5D Mark II is an awesome full frame camera. I love mine. I love the images it produces, but such love hasn't blinded me to the fact that in almost every aspect the D3x is a better camera.

The D3x is nearly 3 times the price as the 5D Mark II, but clearly no where near 3x the performance. The D3x is a studio camera, whos more direct Canon competitor is the 1Ds Mark III. The D3x is a behemoth of a camera for pro photographers who need the reliability and ruggedness that a pro studio body will provide. If this isn't you, then you might want to consider the D300s, which is Nikon's nearest competitor to the 5d2.

As to which lens to buy, certainly if you go the Canon route, you'll have more money to spend on lenses, though which ones to recommend highly depend on what you want to put in your portfolio. Since your question mentions you'll be doing wedding photos, at 70-200 lens is great for close up shots, and for headshots. The 85mm and 135mm focal ranges are very nice for portrait work. 35mm for wider group shots, and a 50mm for normal images. I know that Canon makes excellent lenses in each of these ranges--I'm not a nikon shooter, but I would imagine the same is true with nikon. Note that since both the 5D2 and D3x are full-frame cameras, I'm talking in full-frame focal lengths. If you move to a crop body, you will need to take that into consideration.

Now the real question is: do you really need to consider either of these cameras? Honestly if you are asking which camera should you get, then perhaps neither would be a good fit; consider a body that is geared towards beginners and new hobbyist instead of looking at camera bodies that are for serious professionals. If you are just starting out with a portfolio, there is nothing that either of these cameras can really do for you, that a good entry-level body wouldn't, and for a nearly a fraction of the price.

EDITED TO ADD:

One thing that slipped my mind when writing this answer is that if you are looking to do professional work, such as studio photography/wedding photography, you need to act like a professional. This means being ready for every contingency. Just having a really awesome D3x or a slightly-less awesome 5D2 won't cut it. You will need a 2nd body, possibly even a third backup body available to you. Ideally you'd want to have two of the same body type, to make transition between to two seamless. Can you realistically afford 2 $7000 D3x? Or even 2 $2500 5D2's? Is this a wise investment?

From the comment you made, you'd like to purchase a single body upfront, instead of incremental successive upgrades. I think that's not a bad approach--if you went with the 5D Mark II. I personally believe the D3x is in a whole other class, and unless you can justify it's price tag, it would be likely be more camera than you would need.