Spartan Assault is not a valid option because its not out yet. No way to tell if its the best because no one has played it yet. Troll topic to get people to vote for Spartan Assault. NO one vote for it.
4 was the worst, too much like COD, 2 was my fave,
To the edge of the universe and back, endure and survive
FYI, Spartan Assault has been out for awhile, but for Windows 8/mobile...it will just be new to the consoles. That being said, 2 and 3 are the obvious choices for what they did with MP, both level design and new ranked play.