The Lion King is a technical masterpiece that unfortunately is really held back by some sub-par (voice) acting, singing, and directing choices.
The core story line is 99.9% the same as the animated version. No real surprises here. I was worried about whether Chiwetel Ejiofor could replace Jeremy Irons, but overall I think l he did Scar proud. He, along with Timon (Billy Eichner) and Pumbaa (Seth Rogen) are the clear standouts among the voice cast. On the flip side, Donald Glover really phones it in and is shockingly bad as adult Simba. Beyoncé has no acting chops at all and she isn't playing Nala so much as just playing Beyoncé. The rest of the cast - Alfre Woodard, James Earl Jones, etc - are solid.
Let's talk about the songs which IMO are a huge hit and miss in this version.
The opening Circle of Life was IMO the best of the soundtrack, so the film definitely started on a high note.
I Just Can't Wait To Be King has some great energy and keeps the momentum going. At the end of this, I was feeling really great about the movie.
Unfortunately it is all downhill from there. Be Prepared is shockingly bad as they cut the entire song down to just a speech and 30 seconds of actual singing.
Hakuna Matata tries to recapture some of the momentum but IMO it really lacked the carefree energy the song should have.
Can You Feel The Love Tonight is absolutely butchered. Donald Glover is Emma Watson level bad at singing, and Beyoncé injects way too many vocal runs into her parts. The entire thing just lacks sincerity and sounds like stuff you would hear on American Idol.
Spirit is the new Beyoncé song, and after listening to the full length version on YouTube, it's decent. The problem is that in the movie they cut it down to only a ~30 second snippet so it never even has a chance to hit your emotional chords and make an impact. My reaction in the theater was basically: "Oh new song! Wait... that's it!???"
Overall, they made some really questionable choices with the songs. I think most folks going into this are going to want to see the classic song set pieces recreated as faithfully as possible. And indeed, they did this with Circle of Life, I Just Can't Wait To Be King, and to a lesser extent Hakuna Matata. That's probably why I found those songs to be the better ones. What they should have done is continued to do this so that we got a full length version of Be Prepared instead of this neutered version. Can You Feel The Love Tonight should have been sung with more sincerity (and not in the daytime...). They also should have let Spirit be a full length song so that there is actually something new that folks can take away from this.
That brings me to the directing. In addition to the poor choices with the songs, the film also makes poor choices with many of the scenes. Many scenes like Mufasa teaching Simba the lesson, the stampede, Simba vs Scar's battle, Simba climbing Pride Rock at the end, etc. are literally EXACTLY the same as the animated version. And I stress both "literally" and "exactly"! Such a blatant copy of the scenes just takes you out of your immersion in the film because your reaction isn't going to be what the filmmaker intended, but instead it's going to be "I've seen that before."
Now while it sounds like a contradiction, the reason you can copy the musical scenes closely and not run into this problem is precisely because they have songs! Music can instantly set the mood, and when the songs are playing the audience is engaged via the music so they remain immersed in your film as long as you don't murder their beloved songs. Particularly in the case of such classic songs, most folks are probably hoping you DON'T change too much.
Thus, instead of making some changes to the scenes between the songs and keeping the song numbers similar... they instead opted to make the intermittent scenes exactly the same while making drastic changes to some of the classic songs. IMO this was a serious mistake and should have been the other way around. They compound this by cutting short the one new part they DID add... namely Beyoncé's new song number. Again, I think it should have been a full length song number to inject some novelty into the film. Just for a contrast, whatever you may think of the live-action Aladdin remake and the new song Speechless from that film, they did give it a full 2+ minute scene so that it had enough time on screen for the audience to give it a chance. Heck, one of the criticisms I heard was that they literally stopped the movie so that they could highlight that song! That's a fair criticism, but the point is the film spent time to give the song a fair chance, and from the word of mouth for that movie it appears to have worked!
All-in-all, The Lion King lacks any big defining moments/scenes that you can point to and say "Wow that was awesome!", and IMO it is the blatant copies of classic scenes that is the primary cause of that. Couple that with the hardcore changes to some of the classic songs and that's a recipe for disaster. A couple of the classic songs in the beginning are faithfully recreated and will get you nostalgic, but not to the point where you will be awed like the first time you heard them. Beyoncé's new song is cut down so much that just when you think you might get a new epic song to add to the Disney canon, they pull the rug out from under you. Much has been said of the lack of emotions conveyed by the realistic animals. I wasn't bothered too much by it during most of the film, except during very emotional scenes (e.g Mufasa's death) where the limitations were really highlighted. Ultimately, this new Lion King is more of a whimper than a roar.