I've a 5D mk1 and the wife has a 50D tbh I think the 5D scores on noise (or lack of it) and great images where the colours blend beautifully into each other and despite common wisdom saying the 5D is a landscape camera I personally would say its more portrait etc where you want detail (but not ultimate resolution, although the Mk 2 probably nails that) rather than a typical overview landscape shot. As a landscape camera I dont think there's anything to choose between 5D (mk 1) and a 50D. I doubt the greater resolution of the Mk2 would give it anything over the Mk1 in landscape mode.
The 50D is a better all rounder but 5D images are superb so if you are looking for arty quite detailed landscapes the 5D would be the camera. A wide angle really will be a wide angle on the 5D of course but your 'long' lenses will become 'shorter' and that might be a deciding facor. A 5D 2nd hand and the 50D would cover all bases
Matt
Edit
Scrub that, just done a direct comparison of a fairly wide scene, 5D + 100 macro against 50D and ef-s 60 macro, same aperture/shuter speed etc, the 5D blows the 50 away.