Yep, I think the second shot is the best personally. I'm a big fan of brightly coloured pictures, but I think it's a bit much for my taste in #1 and #3. In the first pic, the cliff looks nice (and even the sky doesn't bug me so much), but the foliage in the foreground is too blurry to have such brightness. It looks more like a painting than a photograph. Same story with #2; where the tree leaves meet the sky on the left side looks weird to me. Again, sort of like green paint splotches on a blue canvas. And in #4, the left side is dark while the sky on the right looks really light, just like D-B-J said.
I stick to film photography myself, but to make the sky look a little richer without overdoing it, I would probably just use a polarizing filter. Or you could just tone it down a couple notches when editing.
...just my opinion. I think the location was really cool, it looks like a neat place!