I'll just do the top 10, excluding Bush and Clinton and knowing nothing of their legacies. In short, if they were fresh faces and running today with similar backrounds to what they had.
1) George Washington- Colin Powell
2) Teddy Roosevelt- John McCain
3) Ronald Reagan- Hmmm... the Gipper would just be himself.
4) JFK- Perhapes Chris Hienz or his own son, JFK Jr.
5) Jimmy Carter- Once again, he would be himself.
6) Dwight Eisenhower- Kinda a Tommy Franks, I suppose, but much larger a figure. Perhapes Franks, Clark and Stormin' Norman all rolled into one.
7) William McKinnley- George W. Bush
Thomas Jefferson- John Kerry... with a pulse.
9) John Adams- Newt Gingrich
10) Harry Truman- Harry Ried, except pro-Iraq War