I'm not familiar with Canon lenses, but the 24-105 is a good lens. Any decently made lens will be pretty good when stopped down to f/8.
I mostly use zooms and it is not really obvious to me that fixed focals would be significantly better, the way I use my lenses. One issue is that switching lenses can help getting more dirt in the camera, dust, metal fragments from the bayonet and so on. That is definitively a plus for zooms.
I carry quite a few lenses normally, a 24-70/2.8 zoom and an 80-200/2.8 (sometimes 70-300/4.5-5,6), I also carry a 50/1.4, a 100/2.8 and 20/2.8 prime. In addition I have a 400/4.5 with a couple of extenders and a Sigma 12-24/4.5-5.6. The primes see little use, except the telephoto and I'd probably use the macro for reproduction. The 20/2.8 is actually a quite good lens, despite it's age, I use it sometimes because the Sigma 12-24 is not terribly good. Having 12 mm on full frame gives some interesting perspective, on the other hand.
To my understanding, the Nikon 14-24/2.8 is the best wide angle zooms around. It seems to match the Zeiss 21/2.8 prime. Unfortunately the Nikon D3X is horribly expensive and Nikon does not have anything competing head on with the Canon 5DII or the Sony Alphas if you need more than 20 MPixels.
i recommend the 5D2 (under no circumstances consider a camera without liveview), but for landscapes i wouldn't recommend the 24-70. stopped down, the 24-105 is going to be as good, lighter and more useful as a walk-around lens, and cheaper. But i'm not much of a fan of zooms for landscapes anyhow - some other possibilities - 50 1.4, 85 1.8, 100 2, 100macro. the wide end is more difficult without spending money - ideally a Zeiss 28 or 35.