Which serious camera would you choose? (1dx/800E/m240)?

Not for sports.
The intended purpose is travel, documentary, journalistic, portraits, landscapes for fun!

Leica M240
Canon 1dx
Nikon 800E

Added (1). I request that people answering not turn this into a discussion of price.

Please also tell me why.

I bought the D800. I skipped on the E since I do not shoot that many landscapes.

If I had the money laying around and did not have to make my camera pay for itself, I would add the M240 to my Leica gear as a digital rangefinder.

I no longer own any Canon gear

I'm crossing my fingers that Pentax will release a full-frame body soon.

The Canon 1D X on the basis of its image sensor. Compared to the others on your list, it's the best. The Nikon is great at low ISO but too noisy, sometimes by ISO 800, only go with the D800 if big prints were going to be made. The Leica is more discrete but might not be as fast or flexible a dSLR.