For what though? He isn't like the other guys wanting to create the perfect world or stop an alien invasion. He just wanted to fuck shit up for a while and be immortal n tingz.
His backstory and methods were a lot more interesting than pretty much anyone other than Pain. Oro was willing to use politics and treachery to achieve his goals, sure you'd fight him eventually but he acted way more like a ninja than anyone other than Pain. Obito started off interesting but the ultimate power thing is boring, especially compared to the power he had before. Plus his motivations were just plain silly: "My would-be girlfriend died so fuck everything!"
Oro and Pain were the best bad guys in the series, they had interesting powers and expanded the world far more than any of the others did.