Prevented a war by killing an entire clan, don't forget that. On the other side we can also say that Minato prevented a war since if he didn't stop Tobi and Kyubi that fast at that time, the militar force from Konoha will have been low and other villages would have tried to attack and kill them, which would have also create another war. So it's the same, but Minato didn't needed to kill innocent
Itachi created a MS jutsu? He didn't created Tsukiyomi since tsukiyomi existed long time before him. He even created nothing since all his jutsus existed before him. The only sharingan users who created jutsu so far we know are Shisui(kotoamatsukami is his own property), Kakashi(kamui is his own property), and Tobi(for the same reason).
Other Uchihas have only receive jutsus that have existed before and maybe they have perfected it or something like that, but never created something