There are some ways in which Narnia is better, mainly as Christian allegory, but it is inferior in a great many others. Tolkien was just better at world-building, deeper in his literary/historical/mythological influences than anybody else who has ever written in this field. https://twitter.com/BecketAdams/status/1254487480520368129

Tolkien was, frankly, a better writer (at least of fiction) than C.S. Lewis. The Narnia books have their moments of brilliance (eg, Puddleglum's speech, Aslan's deep magic), but Tolkien defines the genre for good reasons.

I, personally, would probably rank Narnia fourth among the great fantasy epic series I have read, behind (1) Middle-Earth (2) Harry Potter & (3) Thomas Covenant. All four are tremendous works in their own way, with different strengths & shortcomings.

Narnia is more like the Potter books in terms of its reliance on children as protagonists. It's deeper & more Christian, but also less lively & cohesive as a unified piece of storytelling, shorter on its characters.

Also, the Lion, the Witch, & the Wardrobe is (like the first Harry Potter & the Hobbit) more obviously a kids' book than the rest of the series.

Voyage of the Dawn Treader is easily the best of the Narnia series.

Confession: I didn't much like the Lion, the Witch, & the Wardrobe as a kid, never read the series until I tried with my son, gave up halfway thru Horse & His Boy. Only with my youngest did I get all the way through the series to appreciate the later books.

The Hobbit, by contrast, was the first 'real' book I read, a a second-grader. Tolkien's world engrossed me throughout my youth.