Wilkins is the best one, easily, imo. Great length and athleticism, has natural strength, just needs to be coached up, but it's not like he's a huge project. I think he'd be potentially startable in year two, and projects the best to left tackle of the bunch (although I subscribe to the line of thought that LT vs RT can be overstated).
Johnson is a high floor guy who can play earlier, Shepherd is a high upside guy who'll be a on a longer developmental curve, like Jones and Moore. It's a matter of preference, I suppose.
I've heard mixed reviews about Green this spring. He has a good anchor, and his feet are ok for tackle but would be great for guard. I heard from several people that his body was starting to look sloppy this spring, but apparently he's grown an inch or two over the last few months, which should give him a better chance at sticking at tackle; he actually might be the 6'5 he's been listed at for the last couple of years when he was actually more like 6'3 with a long wingspan. Can probably contribute in year one if absolutely necessary. He's probably #2 after Wilkins, but I'd put him at the top of a second tier with Johnson and Shepherd rather than at the top tier with Wilkins.