The reason i don't think that Narniaweb is the average slice of the population

I legitimately do not think that if someone read all the books and was told to pick their favorite that the study would be the same.

There are always problems with polling.

That is true. The amount of problems with polling is almost endless (the order of the options, the sample size, etc). If you wanted to find out which book is the most favored, you would have to have a very large sample size picked randomly of people who have read all the books (so yeah, Narniaweb not good to be the only source). I agree it's extremely unlikely that the results would be the same if a larger poll like that were conducted. It's really all about sample size and how random the people were picked to take the poll. It would be convenient to have the whole population (e.i. everyone who's read all of them) take the poll but that's almost impossible.
Sorry that's kinda off-topic.
Back on topic, I am actually quite surprised at how many poeple on this site really like VDT, I thought I was a loner

I read the books before most of the homeschoolers here were born. We had never heard of homeschooling - it was something upper middle class people in England might do with their children.

Back to the topic - I like VDT because it's full of adventures, there is so much learning and character development, and there are lots of memorable and loveable characters introduced. It ends with one of Lewis' best wistful moments as an adventure finishes with friends parting.