The 30 Days of Torchwood meme:
Day 30: Why You Love Torchwood

Captain Jack. He was why I loved Torchwood. Hero, adventurer, protector of Earth, omnisexual ex-con, friend (and enemy) of aliens, the mystery man with the wristband... Yeah, I loved Captain Jack.
But there was more than that.
I loved it that everybody's sexuality was fluid and undefined. Every other TV has mostly heterosexual characters, with gay or bi characters being sidelined, or anomalous - in this show, no one was pigeonholed. In the context of the show, Jack wasn't defined as omnisexual, but he was what he was, and he loved Estelle, Ianto, Gwen, the Doctor, tentacled beings - he was very loving.
But it wasn't just Captain Jack whose sexuality was broad. Owen, planning sex with a woman he just met in a bar, says 'what the hell' and goes for her boyfriend, too. Shy Tosh has an affair with an alien woman, and then with an alien man, and a human in between. Even Ianto, who doesn't believe himself to be gay, loves Jack - "it's not men, it's just Jack". The closer you look, it isn't different types of people, it's people loving other people. And love defines itself differently every time.
This seems more real to me than all the other shows on television.
In a simlar vein, the characters seemed more realistic than most, too. They weren't predictable. They weren't simple. They had their quirks, good and bad. Flaws and strengths.
I liked the premise - that aliens are here, and doing their thing, some good, some bad, some ordinary, some inexplicable. I liked the connection with Doctor Who. I licked the sense of quest, which never entirely went away. I liked the sense of scope - that we are part of a bigger universe, that we are in a vast continuum of time, and we are not isolated here on our planet.
I liked the characters. Loved some of them: not just Jack but Gwen, Rhys, Tosh, the other Captain Jack, PC Andy, Captain John.
...And last but not least, I loved the pterodactyl.