After morons forget about him and history takes over, probably the 5th or 6th best. He turned out to be a surprisingly a good Populist Conservative, delivering fairly good on the agendas his constituency ACTUALLY wanted compared to what big business and establishment politicians wanted him to do, especially with the amount of resistance he got from the Left an Right. It remains to be seen if Populist Conservatism will now get a foothold in 2022 and beyond.
If he came up short it was in having to go it more or less alone on illegal immigration, having to rely on the border wall. Then there was his poor professional persona at times through his presidency, especially in poor judgement used to argue the re-election results.
Trump turned economy around, turning it into the strongest economy the country has seen in the last 15 years if not longer (prior to COVID-19) thanks to his use of Supply-Side Economics, including tax cuts and deregulation resulting in, among other things, the lowest Black and Hispanic unemployment on record (again pre-COVID). A number of those economic strengths are still there to fuel the post-COVID recovery if Biden doesn't screw it up with tax hikes and more regulation.
Trump passed tax cuts that benefitted the average working-class to middle-class worker between $500 and $4,000 in tax savings.
His policies allowed the US to become energy independent. This has been due to opening up more area for oil drilling, fracking and some coal production. Resulting in low energy and gas prices. Drawing more companies back to the US in the process because of that.
He has taken on tough problems other presidents kicked the can down the road on for decades. This includes illegal immigration. It includes trade issues with China on issues like American intellectual property, trade imbalances and too much dependency on them in areas like manufacturing, this now on full display due to COVID-19.
He pushed through a major new US, Canadian, Mexican trade partnership (USMCA), eliminating a number of problems with the old one (NAFTA). This put American interests more up front.
He took a very visible stance with the pro-life movement as well being steadfastly behind 1st Amendment religious freedoms.
He took bold steps in the the fight on terrorism, finishing off ISIS, including Abu Bakr al-Baghdadi. He was not afraid to take the fight to the sources of terrorism, like Iran and Qasem Soleimani all without starting new wars the Left was SURE these these actions were going to do.
He's been key in brokering a historic peace deal between Israel and the UAE. All without needing to drag Palestinian issues into it. The Abraham Accords has since grown to include 5 Arab nations and Israel.
As for COVID-19, Trump implemented restrictions on travel from China in January 2020. Liberals literally called him "racist" for doing so. They were the ones who still hadn't got a grasp of the danger presented by the Chinese coronavirus yet, not Trump. More travel restrictions from other regions as well as other actions were implemented soon after. Trump has been ahead of the game from the beginning.
There has been a bigger effort toward making a vaccine than anytime in American history, with government support. Two are now being deployed. More are on the way.
He has been an outspoken critic of the violent social protests from the beginning (unlike from the Left), even pushing the limits of what he was allowed to do about them himself.
His economic policies have brought back a number of manufacturing jobs, Obama claimed would never return to American shores, remember that?
Having a Republican president brought the ability to place Originalism squarely in it's place as how to interpret law in the Courts. Trump did this this well, most notably the Supreme Court with 3 appointments to it.