Hi MDamanda, welcome to the boards. One thing I have noticed around here, is that IT seems to have had the biggest impact on most readers. Even those who say The Stand or The Shining is thier favourite, a lot will say they related to IT most. I would say that having 7 vulnerable kids, each with a flaw of thier own, he covered alot of bases for people to connect with a character - I am sure many fans of IT found themselves thinking "I was the Jew in my group of friends" or "I had the over protective Mother", personally, I was the fat kid (sadly, I am now the fat adult - although thankfully, never bullied at any point in my life). Couple that with some fantastic character depth, story telling, and nostalga, and IT was always going to be a home run.
As for your tendancy to favour books that deal with children, I completely understand. I have said before around here, that is a way to tug my emotional heart strings - have me read about children in distress or emotional turmoil - like the losers from it, Ellie from Pet Semetary, Trisha from Girl Who Loved Tom Gordon, Dinah from The Langoliers, Danny Torrence, etc.
I recently re read It for the first time since it came out. When it came out, it seemed a disappointing ending after such a build up. So I left it alone all this time. After reading what everyone goes on about I decided to give it another go. All I can say is OMG. I think I needed to see the symbolism behind the ending, to mature enough to understand.