No. Kisame would totaly win, either Itachi is sick or not.
1. Itachi needs to use a lot of Chakra to use Susano or Amaterasu. So Kisame would only need to take out a little quantity of Itachi's chakra and he's done.
2. Well... I think every S-Ranked Ninjas know how to get out of a Genjutsu.
3. It's proved in the series that Amaterasu is weak against water, because you can see that the rain turned out amaterasu after Itachi and Sasuke fought. So Kisame would only need to go into water. He can create water, just to remember.
4. Tsukoyomi... Well Kisame could clearly get out of there because Samehada has its own mind, so it could hit Kisame from outside and Tsukoyomi would end. Or Kisame could only use Kai, because he is the second character in "Naruto" with most amount of chakra.
5. Itachi's jutsus are composed of Fire, and Kisame's Jutsus are composed of water.
6. If Itachi uses Susano, Kisame uses Suiton: Daibaku Suishoa, with this Kisame would drown Itachi and Susano or he could only stick into Susano's back and start absorving it, since susano is made of Chakra.
7.Samehada would eat Susano's sword becaus his sword is made of chakra and Samehada absorves chakra.
8. Kisame would only need to use Suiton: Giant Shark Missil (don't know the name in japanese yet) and it would absorve Itachi's Susano or any other jutsus including amaterasu (check Manga Chapter 506 and 507).
9. Guy needed to open 7 gates to kill a fake kisame with only 30% of his chakra (I'm talking about the fake Kisame) and he even needed to use his second srongest attack. To kill the REAL itachi, Guy would only need to open 6 gates because he would get blind and Itachi wouldn't be able to use Tsukuyomi.
10. Kisame is way smarter than Itachi. Kisame belonged to The Hiden Mist Village Intelligence Squad. Itachi only belonged to ANBU. Kisame belonged to The Mist Swordsmen that its like ANBU.
11. Kisame could do a long ranged fight since Samehada can stretch.
12. This is the most stupid argument, but it's certainly the one that its most correct. In ALL animes, ALL the bad guys die from the weakest to the strongest. And Kisame died after Itachi. That only means that he is stronger that Itachi.
13. Kisame is very reckoner. He wouldn't fight recklessly. He just knows how to trap, trick and outsmart an enemy.
14. In the fight against Killer Bee, Kisame said that the strongest the enemy is, the stronger he is. That means, if Itachi is 100% strong, Kisame is 101% strong.
15. Since Itachi is way more famous than Kisame, Kisame knows what Itachi can do. He knows that Itachi needs a lot of chakra to use Susano, Amaterasu and Tsukuyomi. BUT! Itachi doesn't know all Kisame abilities. So Kisame would probably use is superiority in inteligence and would prevent Itachi from using those abilities.
16. Kisame's stamina is WAY bigger than Itachi's stamina.
17. Kisame is older than Itachi, so he has more life experience than Itachi.
18. Hiden Mist Ninjas are trained to be professional ninjas in the art of assassination and killing enemes. So Kisame wouldn't be so reckless like Itachi.
19. Stop saying MS this and MS that. Mangekyuu Sharingan is useless if you don't look at it. Kisame can feel chakra, so he could even fight with his eyes close and he would know where Itachi was and where Itachi's attacks were comeing from. And Samehada would help him.
20. Samehada grows bigger when it absorvs chakra. So Samehada would absorve Susano and turn into a MEGA GIANT SWORD OF DOOM.
