I really don't think so at all, especially since it is wrongfully credited as starting the Disney Renaissance (I'd give "Who Framed Roger Rabbit" and "The Great Mouse Detective" that honor really).
And you'd be wrong.
The Little Mermaid was an event when it came out, and it really did restore the Disney brand. I like the Great Mouse Detective, and it kept the lights on at Disney, but the quality of animation is much lower and as much as I hate to rate films on how much they grossed, it is illustrative in this case: $40 million to over $200 million. The Great Mouse Detective was even outperformed both commercially and critically by An American Tail (made my Disney animation refugees).
Disney was no longer THE brand for quality feature length animation. I'll give some credit to Who Framed Roger Rabbit?, which is sort of a proto-Renaissance film, much like Iggy Pop is proto-punk, foresaging what was to come.
It's also important to see how Disney, a studio obsessed with its own history and mythology, has treated those pre-Renaissance films. The Great Mouse Detective is largely ignore (as is Oliver and company and Black Cauldron, the other two films from this era). Roger Rabbit is at least in the photo, though he's be cast to the side. Ariel, OTOH, is a core character and the foundation of the "princess" brand along with Belle and Jasmine, other Renaissance era heroines (along with the classics Snow White and Sleeping Beauty).
There is simply no reading of history in which The Great Mouse Detective and Oliver and Company, the two films before the Little Mermaid, can be described as the first Renaissance era films. Maybe Roger Rabbit, but that's more of them easing us in to that era of artistic ambition with live action.
Oh, my rankings.
Beauty and the Beast
Honestly, Little Mermaid is more "important" than Beauty and the Beast, but I really want my daughter to emulate Belle, among all of the disney princesses. Bonus points for the best heroine.
ETA: The Black Cauldron is really underrated. But it is considered the low point of Disney's fortunes. So yeah, the Great Mouse Detective is up from the absolute nadir. Though honestly, Cauldron is at least ambitious, Mouse Detective strives for mediocrity and achieves it.
This post was edited on 2/20 at 8:52 am