My brother recently got me into watching the movies and reading the books. (of course this list is still in progress).
Books:
1) The Goblet Of Fire- I loved the idea of the Tri-Wizard competition and it was the first of the books to really go into depth of the character's past.
2) The Half-Blood Prince- Great set-up for the final book although a bit predictable answered a lot of questions.
3)Prisoner of Azakiban (sp?)- Introduced Sirius Black and was a nice break from Voldemort for awhile.
4)Chamber of Secrets- The movie kind of ruined my vision of the book.
5) The Sorceror's/Philosopher's stone- Good Introduction but like ANH a bit slow and dated at times.
6) Order of The Phoenix- Except for the death of a major character mostly seemed like filler.
Movies:
1) Goblet- Now this is what a Potter film should be!
2) Prisoner- A major improvement over the first two.
3) Sorceror/Philosopher- strictly average fare.
4) Chamber- meh!
I know without a doubt that JK Rowling will have a knockout conclusion to the books and I'm sure that will be my new number one.
As for the movies I really didn't care for the first two but the last two were really intriguing, I hope they keep the original cast (even if they do look like their middle-aged by the end of the series) Its also great that each new HP film gets better and better