"We march for Macragge!" Been an die hard fan since I started collecting my Ultramarine army when I was in year 5 in 1st school.
The banners are there, but that doesn't mean all 10 companies were corrupted. "In M32, as a cruel joke, Magnus the Red planted a company of mutated Wolf Brothers on Gangava Prime to ambush Great Wolf Harek Ironhelm and his men after Magnus lured them away from the Fang.[5b]"
Almost went with Ultramarines, but they're already the main face for Games Workshop. I have to cast my vote to the Blood Angels. They are one of the more unique chapters out there. With their Black Rage. I've read many stories around them and have enjoyed their exploits, specifically the graphic novel: Blood Quest.
In the book it's assumed the whole chapter fell, they exterminatus the planet so they can rapidly deploy back to The Fang... or is my memory being all retarded from all those explosions in Iraq?
If pushed I'd say Space Wolves, so they got my vote, but I prefer Raven Guard, White Scars, Salamanders and Imperial/Crimson Fists to any of these "big 4".
It might just be me but I'd rather replace the Dark Angels with Black Templars. Both are medieval-era influenced but the defining differences are that the DA are hellbent on finding The Fallen while the BT are hellbent on spreading the Imperial Truth through their endless, or eternal (yay pun!) crusade.
While riding in their battle barge, the Eternal Crusader... it's so punny. Seems like a no-brainer to me. The Black Templars need to be in this game.