Well...Firstly,I believe Jeremy brett is an extraordinarily talented actor and best for being sherlock holmes...
Secondly the mystery that spreads all over the film is just firmly outstanding in my opinion because the film actually 'begins' with mysterious dreams that holmes experiences ...
And well after all in comparison with the story of noble bachelor this adaptation is really true to life (or to book to be precise) and well the mysterious environment was just appealing to me :)