Favorite characters

I am not good at writing characters or good dialog, so I am hoping to be inspired by my favorite fictional characters and others who have left an impression on me, even if I don't like them. Generally, if even if I don't like them, I'm intrigued by characters who appear to have a deeper untold story, without being obvious about it. If I do like them, it's because they show qualities I admire without being annoyingly goody-goody and/or exhibit a good sense of humor.

• Jamie, Claire, and Collum from Outlander
• Characters from Firefly, especially Mal, Jayne, and Zoe
• Hurly, Sawyer, and Shannon from Lost

The question is, what specifically do these characters do to distinguish themselves from countless other fictional characters? What is the mechanism by which their characters are revealed? What lends them a sense of "realness" (or likeability)? If I can figure out the answer to these questions, I'll be on the right track.