I highly suggest Cutie Pops! The newer lines even have more realistic eyes, and there are some really fun $10 dolls that were just recently released along with a line that's almost always $10 already released. I own 15 dolls, including 4 petities and 2 (original, with swappable ears/tails) dogs, and have plans to buy 5 more as soon as I get paid. If you have any questions about them, I can answer them. :)
They don't have very good articulation (what they do have is nice), but its been hinted that jointed elbow collector dolls will be released one day. Their changeable pops, eyes, and hair are so much fun; when I got my first Cutie Pop I spent around a month carrying her around constantly. I changed her eyes, pops, and hair over and over again (which so far has had not effect on their ability to stay in place, even if I shake her and hold her upsidedown) and had fun every time I did it. I don't remember having so much fun or loving a toy so much even when I was a child, and I'm 20!
I also second Liv dolls, if they interest you at all. Their articulation and posing abilities are amazing (better than Pullips, by far) and they are incredibly easy to 'customize' (eyes and wigs are super easy to change). You can even buy them non-Liv wigs and eyes (like those for BJDs) and since they can wear Barbie clothes they've got a nearly unlimited wardrobe to chose from.