Yup, because despite having like five games about Chinese history in Dynasty Warriors, it didn't prepare use for the idea of playing a game about Japanese history...so they changed it up and made it about demons.
I remember playing it, and really liking it, but going "What the hell does this have to do with demons...?" It's like they just changed the title, but nothing else to accommodate for it.
It'd be like if Godhand got retitled as "Doomsday Dickpunch" in the West because we can't handle such religious subtext in our action titles. Although...I would have been okay with that.
Well Samurai Warriors which was about Japanese history already came out before Sengoku Basara did.
Capcom wanted profitable sales in the west (since Japan was liking the series) so Kobayashi thought it would be a great idea and alter the series in the west and make it very similar to the DMC series (just look at the font of the title) in tone and style.
As for the title and demons, later games included demons such as Nobunaga dying, becomes king of hell, and is resurrected in SB3 as well as his sister Oichi who is possessed by demons and fights using them.
http://www.youtube.com/watch?v=29gpogX3yy8
Now as for the exact game and the changes it went through in the west as Devil Kings, outside name changes from their original Japanese names to simple names (because Americans have low attention spans......I would mock Capcom for thinking lowly of westerners but I'm not sure about Europe but many Americans especially gamers during the PS2 era, and even now, are kind of like that unless if Capcom wanted to aim for a niche or anime oriented crowd but no they were aiming for the same crowd that bought DMC) such as Yukimura Sanada to Scorpio or Ieyasu Tokugawa to....Irdine. Locations got name changes as well from the actual historical location's name to generic names.
The only story detail that was changed was Nobunaga or better yet Devil King. In the original Japanese version he was just some powerful warlord with the title of Demon King but he was just some really uber magician whereas the English version Devil King was a warlord who sold his soul to the devil for power and he is considered the Devil or better yet Satan. The original Japanese version there was no devil and selling of souls he just somehow became the king of hell after dying in SB3. Then there was the backstory behind the game. In game in Japanese focused on the history Sengoku era pretty much while Devil Kings using the same framework just threw another skin on it and the whole war was for world domination and not just one small island country.
Then there is marketing the game in Japan marketed Masamune and Yukimura (mostly Masamune well nowadays that is) as the main characters or posterboy characters whereas the English version Devil Kings marketed Nobunaga as the main character or main posterboy character.
Its kind of like if Capcom brought Street Fighter to the west with Guile being marketed as the main/iconic character instead of Ryu because "MURICA!"
