Monica Furlong's Wise Child as a sort of Secret of Roan Inish quiet, personal, character-driven family fantasy movie or, ideally, miniseries. No big set pieces, action scenes, or fancy CGI, which are all things I like but which definitely aren't suited to the tone of the book, which means it would be hard to market. But maybe that style will come back in fashion soon.
On a similar note, Ursula K. LeGuin's Earthsea books, as the same type of miniseries. Just destroy all knowledge of the previous attempt. (Also, all of her other books except for The Lathe of Heaven because the 1980 film version was already perfect.)
I'd also like to see a re-attempted His Dark Materials, probably also as a miniseries to do it justice.
I don't really like movies as a medium for accurate adapted works, most of the time. They can be entertaining, good in their own right, or interesting interpretations of the source material, but miniseries have much more potential to do justice to long books. Even more than film trilogies do. And TV seems to be where most of the talent has been heading recently.