Janeway seems to be the most nice of all- however I'd have to go with Sisko. Janeway and Picard a close second.
Sisko seems approachable, more like an everyday type of person.
Janeway seems like she wanted to connect with the crew which is not a bad thing at all.
cares about his crew, but appeared somewhat a little distant, not as accessible to some crew members.
If you're talking promotion wise, Picard also seems fair with giving promotions.
He also seemed fair with giving some a fair chance, like the Bajoran ensign from the academy.