Cheeky title aside I would genuinely interested in the answer to that question now that we have so much lore on the heresy, dedicated Primach origin books and all the lot.
More specifically I would be interested whether all the books or the lore swayed peoples opinion towards a specific Primarch that might not align with their chosen faction (granted that person aligns themselves with a particular legion/chapter when playing the tabletop or engaging with the hobby in any other multitude of ways).
For example, say a person is a diehard Space Wolves fan. Is it then the case that said person more often gravitates towards Russ as their favourite Primarch because of faction choice or has the mountain of lore (both well written and not so well received examples) given more context for said person to say: "Well, Russ is great and I love the Space Wolves, but Dorn might actually be my favourite Primarch because of how he was written during the siege specifically"
I know any answer to this would be anecdotal unless we were to do an actuall poll that would be representative. Which, why would you even do that...it's a silly question that some Warhammer nerds might ask themselves. It also might not even be possbile to do properly because the number of people well versed in the lore that could differentiate between the characters might just be too low compared to the entire 40k and 30k fandom to get an actual answer wether the mountain of lore swayed someones opinion on a character or whether someone favours Corax because they simply like Raven Guard.
Also why is the correct answer Sanguinius? Well, it isn't objectively the case obviously, I just included that line in the title because the writers had more leeway to make Sanguinius the bestest, noblest, bravest and prettiest Primarch because his death is an essential cornerstone of the setting. So there are definitely people who can't stand our glorious hawk boy, but I would reckon there are more people with a positive or neutral opinion. Had he not died, more people would dislike him in my opinion, because generally the "bestest at everything" character isn't all that interesting to many readers unless that character dies a tragic death.