It strikes me that one great appeal of the best (from my perspective the best!) fantasy novels, is their depiction of utopia in the sense of not an ideal but a 'good' society - and that this is a thing which is otherwise almost wholly lacking in modern culture.
Tolkien's Lord of the Rings has an unmatched range of good, believable and powerful appealing societies: The Shire, Tom Bombadil's little world, Bree, Rivendell, Lothlorien, Rohan, Minas Tirith - take your pick!
Lesser fantasy fails to provide any such vision of the good life (and is praised by mainstream literary critics for this lack - which they assert, from their nihilistic and purposively-destructive roots, makes it 'dark', 'edgy', 'realistic' and 'subversive' - the ultimate accolade of those who are ultimately motivated by despair and hatred) - and therefore cannot provide what we so desperately need.
Because utopia is a selective microcosm of Heaven, and Heaven is necessary for Hope - and Hope is a necessity for the good life.
What I would love to see is believable and realistic descriptions, creative depictions and speculative discussions on the subject of Heaven; and perhaps fantasy is the best vehicle for this at present.
Heaven has become (and not merely by accident - but also by purpose) unimaginable to modern man. Thus Heaven has become ineffectual: it must therefore be made imaginable, we need actively to imagine Heaven, and to engage with this imagination.