Biden's approval rating right now is 50 percent. Thirty-eight percent disapprove. Obviously, those numbers would be different after a long campaign season, but in which way, I'm not so sure.
Once Trump got the nomination in Indiana, I stopped making opinions on this election, but Obama's approval ratings were like catnip to me. I studied them often, and his resurgence was what kept me sane. Would Biden have gained the same numbers if he had been in the spotlight, running for president? Hard to say, but he's a likable guy.
Many Republicans like Biden, despite the "he's a buffoon" talking point. One of the more moving things I watched during the whole campaign season was an MSNBC interview with Lindsey Graham where he got emotional talking about his friendship with Biden and how awful he felt about his son's death; if you haven't seen it, you really should. Plus, earlier today, Biden got emotional when the Senate renamed a cancer research bill after Beau. Mitch McConnell went out of his way to have the new name of the bill said publically while Biden was present. Politics are politics, but I'm convinced most people who know Biden personally respect him.
At the end of the day, this was a very winnable election for Democrats, regardless of who was running. But mistakes were made. Clinton got cocky in the Midwest, and she often didn't attend rallies there. Pleas for more money and volunteers in that region were ignored. In hindsight, Tim Kaine's debate performance probably should've shed light on Pence, the guy who will often be running the show (if V.P. debates even matter - the ratings were bad for this one). Hell, I'm still convinced Sherrod Brown would've been the best choice for her running mate because he was actually on record voting against NAFTA. Obviously, there were other factors. Clinton's e-mail scandal cut the deepest, and her "I made a mistake" talk didn't work well in the "no apologies" Trump era (but I was personally glad that she owned up to it). Then, there was everything else (the FBI, WikiLeaks, Putin, voter suppression, fake news, etc.), but it is what it is. The cards were uniquely stacked against Clinton, and a good amount of that was her own doing. And a whole lot of it wasn't. And, yes, I'll throw misogyny in there; I talked with a male Democrat a few weeks ago who told me he went for Trump because "women aren't smart enough" to run a country.
Considering the populism that Trump rode in on, the argument could be made that Biden was better equipped to face him than Clinton in the Midwest. But who knows? Maybe Trump still wins. Biden did spend a lot of time campaigning for Clinton in the Midwest, after all. Or maybe Clinton picks Brown and nabs the Midwest in some alternate reality. Or still loses.
Regarding 2020, I don't know if Biden will run. He'll be pretty old, but the primary season would be more interesting with him in the mix.