They said it could never done as movies because it would be too difficult, dangerous, too ambitious and the story is big.
It was once considered to be an unfilmable series of books but in 1977 Rankin-Bass did a successful translation of The Hobbit as a prequel to serve for the upcoming year's LOTR animated adaptation, Ralph Bakshi did an attempt in 1978 which did used a unique old school technique of rotoscoping animation but crammed the first 2 books into one movie but didn't finish it and wanted to do a sequel but was denied. Rankin-Bass concluded the LOTR animated story in 1980 with Return of the King which had Roddy Mcdowell in it, quite a cheesy conclusion.
In 95 New Line got the rights for all three books to become movies Peter Jackson who is a hardcore Tolkein fan decided to do the project and wrote three drafts for each one in 1996 then production began in 1997 to 1998 on costumes, animatronics and technology with casting then in 1999 filming for all three movies at once began. The first movie was released in 2001, the second in 2002 and third in 2003 in December of each year and each got major box-office success with praise from critics and audiences including fans of Tolkein.
I've been a fan of Tolkein all my life since i was 12 about 19 years ago and enjoyed the animated movies since i was a kid and have been waiting for a live-action version of each of the books, my dream came true that in 1998 when i looked on the internet that i was in joy that they are bringing Tolkein's books to film and was overjoyed as it was my most anticipated movie ever.
Saw the first one 18 times in theaters, the second one 20 times and third one 25 times. Even bought the films in both versions on DVD the first day they hit stores and they became instant faves. I love how brilliant the casting is, the effects are, acting, writing, direction and music score are in these films.
Now The Hobbit should complete the story next year and in 2013.