I loved The Babysitter's Club! I think my favorite was Claudia. I felt like it should have been Kristy, but she was so bossy! ;-)
I agree with you. Series books are great if they get kids reading. I babysat a kid who was 6 about five years ago, and he was reading Harry Potter, and he really got into the fact that each book had more pages than the last. He felt like he was accomplishing something by reading them, and I'm pretty sure he's an avid reader to this day.
The nice thing about series reading for kids like me was that if you read a ton, like I did, there was almost always another book coming to keep you busy. I read the Shoes books, and the One of a Kind Family when I was young, migrated into the Christopher Pike books and The Zodiac Club, and a few based in colleges that I can't remember. I love to go to used bookstores and try to find my favorites.