Nice attempt to twist the facts in a way that makes Sanders look better than he does. But really, Sanders would only get +5% on Trump? That's absolutely terrifying and way too close for comfort. Opinions swing wildly during campaigns, and there's no way of guaranteeing it wouldn't turn to Trump's favor.
Meanwhile, Clinton would have Trump beat easily. McClatchy/Marist calls a Clinton/Trump fight strongly in Clinton's favor: Clinton 54, Trump 38, for a +16 split.
What about Bush?
Quinnipiac, on July 30, give the victory to Bush by 5 points. (Buss 44, Sanders 39.) In contrast, in the same poll, people gave the narrow victory to Biden in a Biden-Bush face-off (Biden 43, Bush 42) and the overwhelming victory to Biden against Trump (Biden 49, Trump 37).
tl;dr: Cherry-picking data to make your favorite candidate look good sucks.