I have never liked Thomas the Tank Engine. This is a long-standing dislike, since my high-school babysitting days. My first encounter was through videos while sitting, and I found all the engines to be grouchy and difficult to like. When I got my first library job and found out that they were all morality tales, I just decided that that was why none of the characters were likable and wrote off the series.
Now, of course, I have children. They have Thomas Toys (which I don't mind so much). They like to check out Thomas videos from the library (which I allow, in carefully rationed amounts...and I'm usually cooking dinner while they play, so I can avoid most of them). They like to check out Thomas books from the library. This last week, however, was the first time that we found and checked out an actual Thomas story collection by Rev. Awdry himself. And having now actually read the stories (yes, librarian friends, shake your fingers at me for not doing so sooner or for writing the series off)...they're not so bad. They are morality tales, yes, but Thomas does seem to (slowly) learn from his mistakes and become a more endearing character as the stories go on.
So, it will never be a favorite, but they're not bad. And with all the train vocabulary, I can see why kids love them.