My favorite ME characters would probably end up going like this:

1) Jack ([i]spectacular[/i] character arc, more interesting romance option than most, I thought. Made a badass semi-paragon or truly terrifying renegade, depending.)
2) Kasumi (Loses points because she shows up in 3 less than even Jack. Amusing to talk to and a great teammate for missions, I wish she had a bigger role.)
3) Aria (Badass Asari crime lords are kinda hard to top... wait, this list can include non-crew members, right?)
4) Tali (She's absolutely adorable in a younger-sister type way. Never actually romanced her in any playthrough, just talked and watched her going 'aww, look at her grow up.')
5) Morinth (Why why [i]why[/i] did she get completely shafted in 3? I know you weren't 'supposed' to pick her over Samara, but have you talked to her in 2? She's actually really interesting, like an Asari Jack who never got a chance for redemption.)

Though to be honest everyone's really close. The characters were the best part of the ME trilogy -especially in 3's citadel DLC... everything in there was pure, lovely gold- but those five stand out to me the most.

EDIT: OOoooo, the news will be broken soon.

*watches intently*