When I rank Presidents I do it not just by accomplishments, but also by what they started or set in motion. So Eisenhower is way up on my list for starting the space race, for starting the move to desegregation and civil rights, for starting one of the main engines of our prosperity in the interstate highways. You could argue that several things Kennedy got cred for were really set in motion by Eisenhower.
Anyway, here would be my top four:

Jefferson
Lincoln
Eisenhower
Reagan

No particular order.