Ryujin
Legend
Rey was my favorite. She's obviously very powerful, self-reliant, incredibly fast at learning, and yet I don't think she's in Mary Sue territory. She gets scared. She runs. She is able to overcome those traits, but she still has weaknesses. And that makes for an interesting character.(a big thank you to the force)
I think Kylo Ren was a close second. He's obviously very conflicted, and that inner conflict is an interesting one. He's essentially willing himself to be something that -at his heart- it seems like he doesn't want to be. And for all his power (say, that first scene he shows up in), he's also filled with flaws. From my point of view, that makes watching his development very interesting.
I like Finn, too, but I don't know where he's going. He seems to be overshadowed in basically every area by Rey (piloting, fighting, knowledge about the galaxy), and yet he is still pulled to help out. And that's really compelling, for me. He's closer to the every-man, so he's easier to identify with. And even with all that, he still has fear and flaws that he has to overcome. And he does because of his big heart, which makes him easy to root for.
I liked Poe and BB-8, too, even though I didn't think I'd like either much. I was much more impressed by the new characters than by our old favorites. They blew my (low) expectations out of the water. So, props to Jar Jar Abrams for that.
I think that, with Finn, there are two things going for him. One is as you stated, he's the everyman. He makes a good proxy for the audience. The second is that he's full of possibilities. We know that he's important, but why? Did The First Order recruit from families who were strong in The Force, in hopes of discovering their next Vader? Is it just his knowledge of their internal workings? Is he an undiscovered natural pilot or weapon user?