Just a side note, during that period of time, the Germanic people would have been known as the Goths--there was no Germany, as it was still the Roman Empire. Also, the Redguards would have been known as the Moors back then.
The Romans and the Goths fought many battles for decades, upon decades; both side winning and loser their share of battles. This weakened Rome significantly, but it did not cause it to fall. Rome fell during the 5th century when the Goths invaded Rome and upon winning, the Gothic king declared himself King of the Goths, instead of the King of Rome. That is technically when Rome fell. It is also interesting to note that if you go and really dig into this, you will see a LOT of similar ties between Skyrim's history and Roman history. Just check out Rome, the Visigoths (the ones who took over Rome), the Ostrogoths, and the Moors.
So if we conclude that the Imperials are Roman and that the Stormcloaks are the Visigoths, then we can finally solve the debate regarding who would actually win the Civil War! The Stormcloaks would win because the Goths toppled Rome.
Btw, I'm not just pulling this stuff out of my a$$. I wrote several historical/sociological papers concerning the Romans and this period of history. Specially, I was trying to compare similarities between then and now (imagine that!). The papers were focused mainly on sociological/economic aspects and various things of that nature. However, I did a massive amount of research on this stuff. I actually put several months into the research and notes before I even wrote anything.
Sorry, I wanted to write so much more, but I didn't want this to get out of hand. I tried to shorten it, without dumbing it down. Therefore, if something doesn't make sense for whatever reason, let me know and I will do my best to clarify.
If anything, you can now win the argument if asked to who would really win the Civil War. The answer: Stormcloaks. How do you know? Because they literally won almost 1600 years ago! They didn't have as many resources, they didn't have professional soldiers, they didn't have professional generals, they didn't have "modern" fortifications; they had will, heart, and the ferocity to topple the greatest empire the world had ever seen. And everyone thought Rome would never fall...
-Deacon