OK I had to share this because I think it makes so much sense for why I love Spuffy/ why anyone would be entranced by Spuffy, and why their love is so uniquely captivating and powerful.
The Spike and Buffy journey classically follows the model of the Seven Stages of Love described in Sufi poetry. I don't know why it didn't occur to me before because I actually taught this briefly in a film class at NYU when I was a TA. It
completely mirrors Spuffy, from when Spike first sees Buffy in S2 to his sacrifice in S7, consumed in fire for the sake of his love.
In the classic Sufi tradition, love follows seven stages: Hub (attraction/ first sighting of the love object), Uns (Infatuation), Ishq (Love), Aqeedat (Reverence), Ibaadat (Worship), Junoon (Obsession), Maut (Death). Love is literally described by Ghalib as "an uncontrollable fire that is difficult to ignite and impossible to quench". This echoes Spike's words: "Great love is wild and passionate and dangerous, it burns and consumes." which is a far more profound statement than it seems and he really means it.
Here's a link that explains the seven stages, and there's a video in the link where a song and dance sequence enacts the seven stages from attraction to love, reverence, frenzied obsession, fire and peaceful death (the song lyrics [Satrangi Re] explain this beautifully too - but aren't in English here.) If you read the description of each stage, you really start to see the uncanny resemblance to Spuffy.
Here's the link:
Kaal - Chiron...: Seven Stages of Love
Oh, and I just absolutely have to share this as well. It's the most stunningly beautiful analysis of Spike and Buffy's S7 'closure' ("No you don't, but thanks for sayin' it") from Chosen:
Chosen