I've always played an Imperial and IMO they have as much if not more business being "dragonborn" like the septim line. Honestly play whatever you want but Ive always thought Imperials can pretty much feel right in any TES story.
Pretty much how I see it.
Also the idea of being a Nord just because the game takes place in Skyrim is pretty lame. And Nords bore me. I
may make a Nord somewhere down the line, though. And if I do at all, it certainly won't be before I've played an Imperial, Khajiit, Bosmer and Orsimer...