That alone shows you're inclined towards Nagato and decided he wins before giving the opposition a chance. According to you itachi has 3 skills and is smart... nice.
Getting a bit angry there? It's true we don't know if Tobi had rinnegan prior to Nagato's birth, but it is a possibility, meaning that no one can say it's a FACT when there isn't a clear proof of it. Also, I was not even arguing the fact that TOBI or MADARA
are better rinnegan users, I was was arguing that we don't know if Nagato is the best! Learn the difference please and don't swear in your posts if you want people to treat you with respect. Also it's nice to respect some other opinions, not climb on your nagato-horse and ride it no matter what. I dare you demonstrate that Nagato can 100% beat Itachi and if you convince me I will ban myself from the NB forums.
Also btw, if you want I can be petty. So6P is the best rinnegan user, followed by his son. Dare to prove me wrong.
1. perhaps I didn't, thus the reply. I will look over it again.
2. I was making a highly obvious comparison just to prove a point.
3. No necessarily. I look at it like this: Itachi is smart... if he's got 2 strong shinobi next to him, why risk anything, when they can put an end to the opposition. I know you can agree with me on this one. Why go 1on1 when you can go 3on1...doesn't take Itachi-brains to create that scenario. About Itachi countering CT. I can say Susanoo. The Yata mirror is said to repel all attacks and also to change shape depending on the size of the attack (I'm sure I've read this somewhere. let me know if you need a source). Also a good counter would simply be to use genjutsu prior to that. For example I don't think Itachi has a counter for Deidara ultimate jutsu, but he can still win the fight.
4. Kabuto didn't really counter genjutsu did he? He got caught in one. Also, Nagato has that risk of being caught in izanami, because he suffers from the same case of over-confident-false-belief like Kabuto does. Also, Nagato's weakness seems to be genjutsu. How do I figure? Jirayia was never too strong in genjutsu + Nagato was trapped in one.
5. I was giving it 60-40 to Itachi. I used to think it was a 55-45 before but that izanami pumped Itachi a bit.
Also not sure about the 6 paths statement. It's true that Nagato himself is an easier target for Itachi (though some people seem to thing Nagato >>>>>>>>>> 6 Paths in all situations), but certainly if would be more troublesome for Itachi when going up against all the paths. But 100% win for Nagato is stretching it waaaaaaaay too much isn't it?
+rep btw to you. I stated my reason in the rep.
Without trying to get into yet another 10 page argument for these two (like I used to before it was cool lol) , I need to say that those arguments you've stated are
100% correct and accurate. BUT: it doesn't mean it will work like that. A fight has skill+luck+jutsu+intelligence+terrain+etc involved. Just pointing out that Nagato has stuff to counter the other guy isn't enough proof to demonstrate he can win. I can pick some jutsus from Nagato and give them counters. That doesn't mean Itachi is winning just because he's got counters for soem jutsu. Also y u no counter izanami ? 
I hope we don't get into a further argument about this I keep trying to insist that the fight can go either way but people refuse to believe that. Itachi
has a chance of winning. I don't care how much o a chance because that's up to us to debate, but for whoever says he doesn't, they are wrong. Had to be said.
btw i have to spread some rep before giving it to you, but you get a rep in my book either way. It's not just from this post, but a sum of them.