It depends on what you want to use as a yardstick to measure the best bounty campaign.
More of a subjective approach yes. But most people think of them in terms of the money they bring in and the possible outcome of the MVP of the project. Sadly all ICO projects have ended up being borderline bankrupt or sold off to other companies.
Some bounty has a lot of participants, some offers high payout, some pays with a listed token and so on BUT if you request about bounty that makes their participants happy, I will say NONE.
There was a time when people would eagerly participate in bounties and altcoin tokens would be a subsidiary payment mode in signature campaigns primarily paying in bitcoin. But then the alts died out and ICO turned to bankruptcy and the bubble busted there.
Currently the bounty campaigns need you to do KYC as well, which itself is shady to ask for and without any guarantee that the project tokens are going to be worth it. But some shitposting spammers have to get into them and make sure the bounties last enough.