Why?
FDR rebuilt our economy after you republicans destroyed it, put in most of the banking restrictions that stabilize our economy, started SSI that allows people to retire in peace and so much more. Literally won wwII.
LBJ-Civil rights act, Desegregation, the great society that built even more of a safetynet for people, etc. Very much carried on Kennedy's dream of getting to the moon.
Obama-First black president, Healthcare coverage for all that was fought for over decades, gay marriage, huge advancements in human rights for LGBT peoples, etc.
Woodrow wilson-the fed, huge protections for the worker, anti-trust, etc. Won wwI.
Kennedy-Took the USSR on, put the country on course to go to the moon and pushed for the civil rights act.
Honestly, Nixion would probably be next as he did some good stuff. EPA for one.