Short answer:

Historians can tell you what FDR did. What you think of what FDR did is a political opinion. An American History class has objectively good reason to spend more time on Roosevelt; do not confuse attention with praise. You don't need much Coolidge to write a reasonably complete history of the United States in the 20th century-- but you need a lot of FDR.

Discussion:

Many questions here ask historians to serve as arbiters of fundamentally political debates; that's not our job. History does inform political opinions, and you can find plenty of historians who have strong political views and express them in public fora-- but it's important to distinguish, say "Sean Wilentz as an American social historian, and Sean Wilentz talking about Trump". When politics meets history, we have to clearly distinguish between identifying "things I prefer" vs identifying "things that happened".

When it comes to an historian's understanding of FDR, we can say that he dealt with a very broad range of challenges-- economic Depression and World War being the most notable. We can talk about his political strategies, both domestic and international. These are historical questions which are "true" whatever you might think about the policies he chose.

But for many, the things he wanted to get done are anathema. There were at the time many who along with Charles Lindbergh and his America First movement opposed the US entry into the Second World War, and there still are people who feel that way: they don't think FDR did a good job. Pat Buchanan was among the earliest of the "neo-America Firsters", but Donald Trump appropriated that term and some of the ideology. It appears that we now have a substantial part of the country that's unsure if the War in Europe was a good thing or not; if you think it wasn't then you won't think that FDR was a good President.

Similarly, we have many libertarian/conservatives who are hostile to the expansion of the Federal Government under FDR. Social Security was one of his most lasting political innovations-- there are people who think that was a terrible thing. So Victor Davis Hanson is going to say something very different about this than will Sean Wilentz; those are their political opinions, rather than history.

Objectively, the Roosevelt Administration put in place many social policies to aid those impoverished by the Depression. Some of these policies worked well, others less so. You will find libertarian and conservative writers hostile to social democracy who hate them-- so, for example, see Amity Shlaes 2007 work "The Forgotten Man: A New History of the Great Depression" for an example of this argument. My own read of Shlaes is that this is more polemic than history, but it's out there, and for many folks this will be "my opinion of FDR".

A historian _can_ say that FDR was objectively exceptional in many ways, whether they suit you politically or not. He was President for longer than anyone else: that's objective. In 1944, after having been President since 1933, he won an overwhelming electoral victory-- the public still liked and trusted him by a large margin. You can contrast with Winston Churchill, who lost his 1945 election by a landslide. Objectively, with the War nearing its conclusion, Americans were happier with their leadership and its policies than were the British.

So yes: objectively he was exceptional. Ran the country longer, dealt with more kinds of problems and his policies had an outsized influence on the way the Federal government looks today. If you compare his legacy with that of, say, Herbert Hoover or Jimmy Carter (both very smart and accomplished men), it's fair to say that FDR "matters more". He dealt with issues that few Presidents deal with-- War and Depression. He also was also remarkable in winning election as a visibly disabled person.

His Presidency earns its legacy by the magnitude of the challenges, the importance for the subsequent shape of the American government, the degree to which battles since FDR have been about his policies (for example national health insurance is still being fought over) and his personal political skills. If I'm going to cover American Presidents in summary fashion, its ten minutes for Coolidge, vs an hour for FDR.