As I've mentioned before, it's really easy to find wing back chairs on Craigslist and in thrift stores, but not all are created equal. In fact, Tommy brought up the same thing in an episode of Sarah's House, and I think my husband thought I was crazy when I was saying to the TV saying "yes, I totally agree!!!".
Here is the pair I found on Craigslist and had reupholstered:

(wow, really bad lighting, my walls aren't pink and my floors aren't that red)
Here is what sold me on these chairs:
The Legs: I love when wing backs don't have Queen Anne legs, I'll get to that in a bit. Instead, these wing backs had straight legs and I love that.
The Wings: I LOVE a good, wide curved wing on wing backs. Something that hugs you when you sit in it.
Here are some wing back chairs in the
YAY category:
A beautiful example of a wing back, via the
Traditional Home Showhouse.

This one is currently on the Charlotte Craigslist. I love the curved wings and the straight legs. All the components are very proportionate.

Another Charlotte Craigslist find.. look past the crazy fabric and you'll find some good lines. Even though the legs are Queen Anne, this chair still has a great shape.

Pairs aren't too hard to find. Here is a great pair in Charlotte for $120:

You'll remember I posted these chairs I had recovered for a client around the Holidays. The wings are much smaller than the previous examples, but I liked how sleek they are. The chairs are pretty small, so the scale works.

Okay, here comes the
NAY category. (In my personal opinion) if you see anything like these, keep on moving. I promise a good wing back is right around the corner!
What I don't like about this one: wimpy little wings that aren't to scale with the rest of the chair. Queen Anne legs.. I'm just not a fan. The chair is also too tall and skinny for my taste. I like a wing back I can curl up in and sit sideways.

More wimpy little wings. So sad :(

I like a wing back with substance, but this one has TOO much substance. Looks like it had few too many girl scout cookies (which I am totally guilty of lately, by the way).

I don't HATE this pair, but I don't love it either. I'd probably keep looking (and be super excited when I found the pair in the YAY category).

I hope this helps.. I realize there are very subtle differences between YAYs and NAYs and I hope I didn't confuse you!