FDR made America a much better place to live over a period covering more than a decade. The only obvious blemishes are Japanese internment and court-packing efforts, but those pale in comparison to the sheer impact of all the good things he did.
FDR saved Western-style capitalism, by forcing the creation of a social safety net and a degree of worker inclusion in its benefits, and by putting limits on capitalism's ability for uncontrolled profit-seeking that harms everyone.
FDR also pushed for very damaging laws that prolonged the Great Depression. Sure, his leadership during WW2 puts him in the history books, he pushed for some extremely important reforms and it's only humane (and sane) to build a decent safety net, but the Japanese internment was extremely evil and his economic policies often didn't work out. Like I said, I'm all for establishing a safety net stimulating the economy during a recession, but FDR pushed for some idiotic policies. Austerity in 1937/1938, anti-competition measures with NIRA in 1933 (which was declared unconstitutional in 1935 but by then the damage was already done), anti-competition policies in general (which continued after NIRA was deemed unconstitutional). FDR's economic record wasn't 100% successful.