Well, Tsunade doesn't necessarily have a "sage mode", and, while humorous, Sasuke definitely doesn't. Amongst the rest, we can certainly say that Jiraiya's isn't the best because Naruto perfected the toad sage mode, and Jiraiya didn't. That brings it down to Hashi, Kabuto, and Naruto. I would say that Naruto's SM is the worst amongst those three because it only confers more chakra and toad kumite. Kabuto's SM seems very powerful, but many of the powers he displayed were a result of the DNA he incorporated into himself, not the sage mode itself. Therefore, I'd say Hashi's is the best.