You have cherry-picked some guys who support your idea while leaving out some who don't. The fact of the matter is that Tulo, Hawpe, and Atkins were all pretty good (Tulo VERY good) when they played for the Rockies, which was in their 20s when you'd expect a typical player to be his most productive. As all three entered their 30s their skills declined, as most players' do... and if you look at their career stats you will see that with all three their decline began in Colorado, and continued after they left. The Rockies noticed this and traded/released them. Leaving an offense-friendly home park definitely had something to do with it, but it wasn't the only factor in these players' decline.

On the other hand, we have players like Fowler, Holliday, Ianetta, and Dickerson who have done great things for the Rockies and then moved on. Home/road splits normalized, and they remained much the same as they were when they were here. Coors Field may magnify a player, but it hasn't created many.