First ever would be CS Lewis' Narnia stories - but of course, he and Tolkien were great friends so may have influenced each other. More recently i have been delighted by Terry Pratchett's Discworld - so well-realised without being overdone ( so many "fantasy" worlds are terribly samey, especially now i have read Diana Wynne-Jones' "Rough Guide to Fantasy"). I used to love the "Oz" books, haven't read them in years but saw a fascinating BBC programme on L Frank Baum recently - hadn't realised what an innovator he was in terms of characterisation.