Jeb would have the stigma of being the relative of two losers, he certainly wouldn't be the frontrunner now matter how much the Jeb fangirls think he would be.
First of all, the question here was about George W. Bush. So, Jeb would be the son of a Former President who is now well respected, and the brother of the 2000 Republican Presidential Nominee who lost the closest election in history.
Secondly, he'd still have has impressive resume, his vision, and his fundraising ability. The establishment would support him still, and as I have pointed out on numerous occasions, other than 1964 and 1980, the establishment has always gotten it's way as far as presidential nominees.
And has produced terrible presidents for the exceptions of Harding and Coolidge.
Please explain how Harding was a better president than, say, Eisenhower.