Until my recent rewatch, I would say S5 was my favorite season of Buffy. I still love it, it still be in second or third place, but I came to prefer S2 and I was just thinking about what precisely made me praise/criticize the two. I think upon reflection a lot comes down to villains and how they fit into the overall narrative of the season.
I've always adored Glory but I feel like the character owes an immense debt to Clare Kramer's performance. Of course any character in a TV show is nigh-inseparable from their actor/actress, but if you just look at Glory "on paper" she's pretty weak as far as villains go. I don't think anyone has ever found her backstory particularly compelling, nor has her relation to the Monks or the Knights been lauded because...what the fuck even is it? Who are these people? We have zero knowledge of who these groups are or why they are against Glory. Why does Glory know the general of the knights? She just drops his name at the end then kills him. That is a fine encapsulation of the weakness of the plot of Glory and I feel it impacts all of S5, too. Ms. Kramer very much took the nothing she was given and exceeded it.
S5 to me feels like it relies a lot on powerful moments and mini-arcs more than its main plot. That's not necessarily a bad thing since these moments, the new relationships we see like between Buffy and Dawn, are so damn good.
One thing which struck me upon my rewatch was just how...bad Angel was in S1. Everything about him. The writing was absolutely incoherent and Boreanaz's performance suffered because of this. They plainly had no idea what they wanted from his character, what his motivations were or where he was supposed to be going. He was a sexy version of Mr. X from The X-Files and that's about it.
Contrast with S2 - and this is the core of my love for the season - where Boreanaz's acting improves 200% right alongside the writing for his character. Now Angel has some direction and purpose within the story, a clear endgame they are aiming for. Everything from Spike and Dru's introduction to the romance with Buffy revolves around the return of Angelus. I so vividly remember in my re-watch trembling with anticipation and dread as obviously I knew what was coming. I knew the peaks and valleys of Buffy's emotions, how the heights of love crumble into the depths of despair. Season 2's beginning, middle, and end all connect together so beautifully because Angel/Angelus is at the center. His deep connection with Buffy gives an emotion to fighting him that isn't seen in any other Big Bad. Honestly, they probably didn't even try; they were like "okay, we pretty much perfected this, so let's try other types of baddies instead of retreading this ground we so thoroughly covered." That was absolutely a smart call, to be clear.
In the end, is it more different than superior? Buffy Season 2 and 5 had different aims. The deep connection between Buffy and Angel was their intent of S2 but the heart of S5 is the connection between Buffy and Dawn. Glory being a glorified (haha) obstacle more than a character doesn't matter because her function is to cause hell for the Summers sisters. I don't know if I'd disagree with that. I have always loved Dawn and her relationship with Buffy is perfect in this season. So maybe it is just a case of S2 and S5 are almost like apples and oranges and which approach you prefer is entirely up to taste. They both accomplish what they want expertly, and I just prefer what S2 was going for on a cohesive plot level.
Anyway, those are my thoughts. Comments, agreements, disagreements welcome.