Though I am a Black Templar all the way and I love my primarch to death, Sanguinius was the best of them. His personality is awesome which is fitting since apparently he's the most similar to the Emperor, although I think he'd have a harder time getting shit done in the manner that E-Money did.
Leman Russ is the worst of the Primarchs. I think the best are: Alpharius/Omegon: they manipulated the entire heresy to ensure the defeat of chaos, and even though they failed, they continue to mess with the other traitor legions. Magnus the Red: an utter badass, being on of the only Primarchs to get things done. He likes long walked on the beach and killing Space Puppies/Space Wolves
Magnus the Red for me. He is aware of everything and has the patience and planning to make the one strike count. Though not so cool how he treated Ahriman after doing the Rubric though.
magnus isnt the only one to get things done:dominion of fire, second war of armageddon (i think) all done by angron, angriest mofo in the warp!
Sanguinius no dubt. He was all the Imperium wanted to be. And even in death ,his strenght still blesses his sons when their lasts battles ,in the form of the Black Rage. His imprint on the gene-seed of the Blood Angels is not a flaw ,but a strenght!!!
I'd say Ferrus Manus for these reasons. Loyal, Fulgrim was the Primarch who he was the closest with and instead of joining him he stood by the Emperor. Also defending Fulgrims flagship at the cost of his own marines lives well before the heresy by placing his ship in between the enemy and Fulgrims ship. Reliability, like the Iron Hands bionic replacements, (although that was something Ferrus wanted to remove) they could always be trusted to get the job done. Endurance, he killed the silver wyrm by drowning it in lava which would have undoubtedly been hazardous. Strength, Either he or Vulkan can claim the title of strongest Primarch. Self-conscious of weakness, always striving to improve himself and his legion. One of the few Primarchs who knows his place in the Emperors plans and follow them as best as he can. Great craftsman and values both destruction and creation. And being the first martyr in the Horus Heresy, martyred himself so everyone could see how far the treachery had spread. Thats why I think Ferrus Manus is the best Primarch.
Sanguinius, His body was most altered by the warp when they were taken but his mind was the Purest. Just as tactically intelligent as any other loyal primarch, Flight, before his brothers began to fall they all adored him, even horus and others who were leaning away from the emperor loved him, there were fights between the other primarchs over any number of things, even rivalries between loyal primarchs but all of them loved Sanguinius
