Its a fun debate. When I was a kid, BTTF II was my favorite because let's face it, the future is cool and as a child of the eighties the flying cars and hover boards were enough to keep me interested.

Now as an adult, I still really enjoy the second one, but more for nostalgia and I always enjoy movies or literature that is set in the future and then we actually get to see how far off they were in the way they portrayed the future. We're less than two years from the date used for the future and there are obviously ways that they over projected i.e. the flying cars and hover boards, the complete control over the weather, the pizza hydrator etc.(and the Cubs being good )there are also examples of where they under projected like fax machine still being prevalent. I also really like when watching a movie set in the future you can see obvious hallmarks of the era in which the movie was made. Like looking at the fashion or auto design trends in BTTF II, its obvious the movie was made in the eighties. I really enjoy the translucent tie worn by Doc and the side by side ties worn by Marty and Ito.

Regarding the entire series, I still prefer the original.