Darth vader.

Dooku and it ain’t close. Man has a real understanding of political issues to push the successful propaganda campaigns he did, and constructed a functional government in two years. No one else here has a fraction of that competency.

Dooku would be effective.

Just not benevolent.

Um… who here would be benevolent? At least Dooku had a former care for reform and progress, that makes him very front of the pack.

Count Dooku here is the only one who has a coherent vision for the Galaxy under his rule. Both Vader and Maul want to rule the Galaxy as a consequence of dark side power-madness and little else. Tarkin is just too ruthless and uncharismatic for the job, Pryde is a military commander but not a politician and the same goes for the Droid General.