Yes Sullivan is the "best" in terms of highest ratings. On the Republican side, GHW Bush has the best overall numbers of initial candidates. There are other factors that make a candidate "best," some of which are the "special traits" they have. GHW, for example, gets bonuses for NAFTA, Globalization, and Tax Cuts. FDR has a boat load of "special traits."
Pick a running mate that makes up for your pres. candidate's weakest traits. With Sullivan, pick Edwards (the second-highest rated player). You can run with Sullivan/Edwards (and later Sullivan LBJ) until you get to FDR or TJefferson. On the Repub. side, run GHW Bush with Laura as VP for the best numerical combo.
P.S.- Washington's ratings=wow!