I think there are two ways to address the first question. One is, which series' third season had the best episodes in terms of Star Trek
as a whole? For that, I guess I'd agree it's TNG, though DS9 is a close second. The other is, which series had the strongest third season relative to the rest of that particular series? In that sense, I'd give it to Voyager
. Season 3 was my favorite season of VGR, with a lot of strong, solid Star Trek
stories. Season 4 was comparably good, but season 3 was the only one that really managed to be the show that Voyager
's creators wanted it to be all along -- i.e. a show that was less about the obsession with getting home to the known and familiar and more about embracing the adventure of discovering the new and unknown.
As for who'd be the best person to cheer me up, make me laugh? Definitely not Quark. He's someone you can find funny watching him from a distance, but I think his insincerity, selfishness, and impatience would make him less comforting to someone who actually had to deal with him face to face. Neelix would be much better as a source of cheer and comfort. Yes, he has his idiosyncrasies that can try one's patience, but he's very sincere and genuinely good-natured, and it's a lot easier to believe he'd really have your back when you needed someone.
Dr. Phlox would also be good for a pick-me-up. He's irrepressibly good-natured and a lot of fun. In terms of being intentionally funny and able to make you laugh, though? I'm thinking either Kirk or Jadzia.