Just beat it. Jack and all the NPCs died because Illusive Man told me to make sure I'm prepared and I did three too many missions. Goddammit
I don't miss Jack though. Told her to eat carpet during the Miranda fight. Fucking laughed when I read her poetry in the Shadow Broker's lair. I thought bringing her to the final battle would protect her from dieing on the defending team but Bioware was a step ahead of me. Ah well.
Mordin's definitely a favorite. I thought Garrus was already really likable in ME1 so seeing him toughen up in ME2 was pretty awesome. Tali was just adorable and only really creeped me out once she became perpetually horney (she sounds like an erotic novel character once you decide you're gonna fuck, and she googles "Human Mating Rituals" regardless.) The Shadow Broker DLC blew my mind and made Liara actually likable, and I dunno what'll go down in ME3 since I told her we're gonna have blue children then proceeded to unmask Tali.
Legion is really interesting, I thought. Mostly because his very existence is so weird and hard to understand. I really don't fully grasp him. I was pretty torn on what to do in his loyalty mission. That and the decision on whether to keep the Collector base actually had me alt tab out of the game and think about it for awhile.