In an actual VS scenario Obito has a chance at both of them, not at the same time of course. But in Kishi's manga then yeah, those two are better. Also, you fail to mention that Madara took everyone other than Hashirama lightly, it's that Uchiha obsession he has.
Same goes for Itachi. In a VS scenario he's basically unstoppable, plot-wise, he's not in the top 5.
That's not my point. My point is that Kamui isn't invincible, and Konan could've possibly had a small chance if Obito didn't have Izanagi.
Yeah, with all that prep time, careful planning and countless number of simulations of course, but without any of that, she barely has a chance.