I'm very unhappy with Roberts, but as far as GWB being the worst Republican President, remember that his father gave us Souter, Eisenhower picked Earl Warren, Ford gave us Stevens, and Nixon put two liberals on the Court.
It's too soon for an overall judgment of Roberts, but this may be his Dred Scott case...the one case that history vilifies him for when everything else is forgotten.
I have been outspoken in my belief that Bush was a horrible President, in that he refused to defend himself and gave us Obama, in the TARP, in his prosecution of the war and letting the libs play the "Bush Lied" game without any response, and in his spending, among many other things. But I don't blame him for Roberts. We all thought Roberts was a great pick at the time, based on what we knew of him. Unless Bush knew something we didn't, which is unlikely, Roberts seemed like a good choice, and up to now, has been pretty much what was expected.
But now, he is dead to us. I hope he is impeached after the elections and we get a new CJ. That would be a good first step to restoring the Constitution.