WWII is definitely the best war to learn about and by that I mean they overly teach you about the American Revolution, Civil War etc. I think I've spent at least 3 years of history learning about late 1700's to the late 1800's and after a while you just get bored of it. So far I've learned about 2 weeks worth of WWII, that is just in school though.
Well this seems sad but the periods that would interest me if i took the time to investigate would be the Roman Times. The way thier battles went, how they over came situations even the fact that they had control over alot of population.
Even though they were ever so bloody they still stand as one of the best conquers in history and for that I respect them as well as them having influenced most of the world.