Yeah, I would agree that Vietnam is worse than getting a BJ. But the criteria isn't "whose worst failure is worse." It's who was the better president. LBJ accomplished much more.
GWB had the exact same policies as Trump has now....except, in handling the economy and domestic affairs, Trump is more GWB than GWB in every way: more reckless tax cuts, more inexplicable deficit spending, worse attacks on workers and union rights, more deregulation and corruption-enabling, way worse appointments of crooks, industrial lobbyists, and corporate hacks. And if Trump had GWB's popular support for intervention, he'd probably have already intervened in Iran and Venezuela.
To say GWB was the worst modern president but slobber all over Trump is the height of stupidity.