Can Tobirama Beat Kisame?

Kisame could do most everything Tobirama could do in regards to Suiton jutsu, just to a lesser degree. And it wouldn't be much of a fair fight if the two weren't at their very best, meaning Kisame would have Samehada and would be as strong as he was when he started the fight with Killer Bee.

Is Kisame a better water user than Tobirama?

What makes Tobirama the best water style user is the fact that he doesn't need a water source for his jutsus, while Kisame needed to create a water source on his own with another jutsu to be able to use them (other water style jutsus like shark bomb) on dry land. This was seen against Guy and Bee.

Who can defeat Tobirama?

2 CAN BEAT TOBIRAMA: HIRUZEN SARUTOBI

Hiruzen surpassed his teacher in all aspects and rightly earned the epithet of "God of Shinobi." A huge testament to Hiruzen's skill is the fact that even in his old age, he was able to beat Hashirama, Tobirama, and Orochimaru.