I think this pretty common. I refused to read the books until after the 2nd movie. I thought the 2nd story took the "gee-whiz" element of the first and actually started to tell an interesting story. (This comment probably belongs in the "sequel/sequal" discussion Boost and I are having in the other thread.)

So my wife and I read all of the books (4 was out at the time, if memory serves) and I immediately disliked 3. I thought it was

a. missing critical information that made the denoument make sense.
b. Hyping style over story
c. Dismissing magic. The lack of "school robes" and their replacement "street clothes" and Mike Gambon, I thought, was a poor replacement for Richard Harris, especially as he (and the director?) were set on rebooting the character at the same time.

Rewatching HP1 the other month with my kids made me think maybe Richard Harris wasn't as perfect as I remember him being... but that was my thought at the time.

4 was sort of 'meh' to me, even if it had been a little bit since I had read the book. 5 was awesome to me (longest book = shortest movie?) probably because it had been long enough that I had forgotten what was in the book that I could enjoy it again. I think 6 was decent enough, but I had to ask my wife what the deltas were.