because they're protagonists
Antagonists, really.
And this thread does raise a great question: Why are the Uchiha so damned strong? Even somebody who doesn't seem that great like Obito suddenly turns around to become one of the strongest ninja in the world. Madara probably IS the strongest ninja on the battlefield right now. Sasuke is probably up near the top of the list as well. I mean, does anybody here doubt that Sasuke is now stronger than Kakashi, Gai, and many of the kages?
And we all remember how powerful Itachi was. Even when he was sick and half blind he was still feared and respected among Akatsuki and other ninjas as well. In the fight against Kabuto, it certainly appeared that Edo Itachi with regular MS was just as powerful as Sasuke with EMS.
I guess if we put things on a bell curve, we can say that in any population of 1000 people there are going to be people who are "one in a thousand". And obviously, since the clan is almost completely destroyed, only the ones from the very top still survived. The problem is, Itachi massacred half of the clan by himself, so we have to do a balancing act. The more Uchiha there were in the clan, the weaker they needed to be on average (because Itachi killed half of them by himself), and the more statistically unusual people like Itachi and Sasuke (and Madara, and Tobi/Obito are).
Let's give some examples. Let's assume that only about 1/5 Uchiha are warriors, the rest are women, children, the elderly and non-combatants (chefs, teachers, librarians, etc). Let's also remember that Madara/Tobi killed half of the clan. That leaves one fifth of one half of the people for Itachi to fight:
1) If there were 10 people in the clan, Itachi needed to kill 1 warrior, so Itachi is stronger than 1 Uchiha
2) If there were 100 people in the clan, Itachi needed to kill 10 warriors, so Itachi is about 10 times better than the average Uchiha warrior
3) If there were 1000 people in the clan, Itachi needed to kill 100 warriors, so Itachi is about 100 times better than the average Uchiha.
(we can decrease the numbers further if we assume Itachi killed some of his biggest threats in their sleep, etc)
See what I mean? The level of population for the clan determines how strong they must be on average, and how unusual Itachi is in comparison.
(TL;DR) IN OTHER WORDS, it depends how big the clan is. If there were less than 100 clan members, it's likely that the clan
IS OVERPOWERED, because all the warriors would be more or less as strong as Itachi (in the same ballpark). On the other hand, if there are more than 100 clan members, they are probably
pretty weak on average, and only a rare few of them are overpowered. With bell curves being what they are, the more clan members you have, the more statistically likely that you're going to get an outlier more than one or two standard deviations away from the mean (but then again, the lower the mean would have to be to make the numbers work).
