I'm bored so I'm gonna rank the arcs I've seen/read of SAO (which is up to the end of WoU)
6. Aincrad
5. Fairy Dance
4. Phantom Bullet
3. Alicization
2. Mothers Rosario
1. War of Underworld
Honestly Reki's writing improved so much throughout the series and it's fairly evident-

-Aincrad arc felt rushed and that was because of the restraints Reki was under while writing it so I can't really fault him-fairy dance is one of the most hated arcs in the series but honestly after rewatching it I have little problems with it-

-Phantom Bullet arc was a huge turnaround for many people because it's no longer "Sword Art Online", per say, (an irl friends words, not mine) but I never really had a problem with it. It introduced a cool character and provided a good amount of character development-

-I'll be honest, I was iffy on Alicization AT FIRST. I thought it was going to be a whole new show with an entirely different cast (excluding Kirito), but I was wrong. It focusing on both the real world events and the events of the underworld was nice to watch. I enjoyed-

-the new characters, Eugeo is one of my all-time favorite anime characters (plus he has cool ice sword)
Unfortunately Kawahara has a habit of introducing good characters and then ending them ahahaaha...
*cough* moving on-

-Mothers Rosario... I can't really find why exactly I find it better than Alicization.. I guess I just overall enjoyed it more. Yuuki was a great character who unfortunately fell victim to the Kawahara curse.
It also proves that Asuna is more powerful than many people think-

-That's all I really have to say about it. I can't really dive into War of Underworld to avoid giving spoilers so uh, yeah...

I could honestly make this thread 10× longer by saying even more things I love about this show but I'll spare anyone that. I'll just say I love this show with all my heart and leave it at that.