I'd probably go with Clinton, but not with a whole lot of conviction or certainty. Many of Clinton's flaws bothered me less than some of the others, and on policies I tended to agree with him a lot, so that might skew my answer a bit. If I really disagreed with him more, I might not put him first.
Reagan was incredibly effective and influential, but some of the influences have been pretty horrific, and I think Republicans putting him on a pedestal alongside the biggies like Lincoln is really dumb. He could be my no. 1, but I feel like I'd want to add an asterisk or something.
Obama's another odd one for me, because when I think back, substantively, in eight years, it seems like he had two major accomplishments, cleaning up the economic mess that was dumped on him and Obamacare, which pushing through ended up making it impossible to get anything done legislatively after that.
Trump is still working at destroying Obama care, and is pretty much still making reversing Obama no matter what the issue is one of his priorities, so I feel like, by the time the Trump regime is deposed, Obama may well end up being remembered mostly for being the well spoken black guy that scared America so badly, we elected Trump.
I hope I'm wrong about that, and using think it's justified, but I feel like even a tiny bit of blame for enabling the Trump presidency may end up overshadowing everything else.
Carter, I always liked, when I disagreed with him, and the guy was sharp, but not a great President. I sat in on one of his classes, though, and feel like, maybe if he'd had the benefit of coming after Reagan and Bush like Clinton did, he might have been really good.
Bush 1 I personally liked, but being President wasn't his gig, and he seemed to lack the leadership and personality to do much more than trail on Reagan's coat tails until Slick Willy dazzled everybody with superior style.
Bush 2 was probably well intentioned, but 911, Iraq, Afghanistan and Katrina really screwed him up and anything else he did or didn't do will likely be forgotten.
And last, there's Trump, whose deeds are still being done. He's at the bottom of my list, but, in terms of influencing the country and changing the course of history, he may still end up with the biggest chapter in the history books. I hope I'm wrong one that one, or that the backlash is what he's remembered for.