Okay, that's just wrong. Itachi can potentially beat Naruto with Tsukuyomi. Nagato will be wasted because he can't move and his defenses are reflex-based (unlike Susano'o, once it's up,) so Frog Kata will break his neck. The only way Nagato stands a chance is if Naruto is retarded and uses chakra-based attacks knowing full-well they won't work. Just like how he ought to know not to look at Itachi's eyes. Neither stand a chance against him if he actually uses his abilities logically.
If we're talking about Obito at his best, then once again, Nagato has the short end of the stick here as Obito and his own Pain can pretty easily get Nagato to brun his interval than quickly warp him. Or Izanagi is a flat-out guarantee. However, if Itachi sealed just one of Obito's Paths with the Totsuka, then Obito's plan would have been ruined, so it's unlikely Obito would risk fighitng Itachi. And Itachi is also the one with a solid counter to Izanagi.
Not to mention Nagato's never been shown to be particularly good at using his abilities.
Kabuto pulled the big guns out immediately. Nagato, whether before Kabuto took control or was using Pain, always progressed slowly with his powers in battle. And while his abilities are better fro greater numbers, Itachi has a number of hyped abilities that are ignored, such as being able to control powerful ninja or multiple entities at one time.
