people on this thread are underestimating kisame :/ he forced Gai to release the gates on a 30% portion of kisame and easily captured his whole team with a water prison that only the byakugan can release him from and if naruto were to try and release himself, he'd have to summon the kyuubi chakra which would easily get absorbed by his samehada.
Also, we have to take into consideration of their battle styles. Naruto fights head-on with the exception of his FRS that can be thrown but deals considerable damage towards him, so he won't be spamming that but kisame on the other hand is versatile in his range. He can attack from all ranges and even change the terrain into water in a meer seconds that will cause naruto major problems and with the technique that he used on killer bee that nearly killed him, i don't see naruto getting out of this technique quickly.
On to sage mode, it needs time to activate and doesnt last long. Kisame won't lie down and wait for naruto, no way. He will be up in naruto's face with assault after assault and even with the boost of sage mode, Kisame (with his huge chakra reserves and brutal strength) would witstand it to an extent and counter with something and once sage mode is done, he can only rely on the kyuubi chakra which is easily absorbed by kisame's sword.
It all depends on the scenario, if they're prepared or if its a suprise attack. All fights shown in the anime, one participant has advantages over the other and that can easily change the tide of the battle.
If it were a straight-on fight i think Kisame would win but this is naruto, he won't die to kisame obviously. U_U