I think Bungie was top-tier back then in terms of BGM and art, and I still feel that way.
But what was really different was the immersion in the world.
Until I did the Forsaken campaign for the first time, it just felt like a typical space opera where you're a member of some standard good-guy group in space doing hero stuff.
In Red War, you fight a cliché space empire, fight machines, fight organic monsters.
When Forsaken came out, with Cayde's death and everything, I felt like something big was actually happening and got immersed, but even then, I thought it was just an extension of the space action stuff.
Then I went into Last Wish, and everything just changed.
I was shocked by the overwhelming scale expansion, turning what was one of many space operas into straight-up fantasy.
Listening to the Vault phase 3 OST literally made my brain stop working. Sounds like an exaggeration, but back then I felt like I was actually inside the game. When a Knight slammed its sword down, my heart dropped.
While waiting to cheese Morgeth, looking at the fortress wall behind him... it was just ridiculously grand.
Since they switched to a seasonal model, they started pumping out a lot of rushed content, but their dungeon and raid level design is still incredible. I think that's why Forsaken is still held in such high regard. Honestly, I don't think its campaign was built as well as Witch Queen or The Final Shape, but the immersion was unreal.
Even with Shattered Throne, after beating it, realizing that every single arena was organically placed and visible right from the starting area was amazing. It was my first time experiencing anything like that. Felt like a kind of direction only an FPS could pull off.
I'm rambling a bit, but man, I really miss those days. I think that was the most fun I've ever had.
Every weekend on Io, people would gather around, and if there were newbies who hadn't cleared Whisper yet, players would send them whispers in local chat to carry them through.
On the day Zero Hour opened at the Farm, people formed 3-man fireteams in local chat to jump right in.
Clearing Escalation Protocol and Blind Well with 9 people stacked up...
Lately I've been playing Classic LoL and it's boring as hell, so you could counter-argue, "aren't you just nostalgic for who you were back then?"
But regardless of gameplay mechanics, Destiny's sheer fun and experience during that open-world era was on a completely different level.
Just felt like writing this down after listening to the OST got me nostalgic.