1 is good but I would trim just a little off of the sky to put the horizon closer to a 1/3 line. #2 is good also, but I would remove some of the blue cast to the hazy background. If using photoshop, open a saturation layer, pull down the blues and cyans to need and then create a mask, press CTRL+I to invert and then with the mask highlighted, paint white over the areas where you want to apply the de-saturation. #3 is too heavy on the contrast to me and also has the blue colorcast #4 while a nice concept, I think the tree dominates too much and for whatever reason just doesn't seem to work for me. Maybe its just the framing of the entire shot, not sure. Nice effort at doing something different with the grand canyon shots though.