Pedantry Time!
LOTR isn't a trilogy. It's a single book divided into three parts. By definition, each individual part, of the three, has to be able to stand on it's own with out the other parts for a work to qualify as a trilogy.
As for the film versions, I thought the first one was excellent, but the second was weak. I'm hoping the extended edition will be better. As a fan of the book, I really don't have any problems with the changes to the events in the translation to film. Most of them were to be expected. The complete re-write of some of the characters' personalities (Merry, Pippin, Elrond, Faramir, Gimli, et al) does bother me. The changes were unnecessary (lame jokes involving Gimli or making Elrond a bigot do nothing for the pacing or length of the films nor required impossible special effects) and were a disservice to the characters (Faramir was made into an a-hole).