As someone who spent a ton of time playing UO, I really wish there had been a way to capture the experience of running various dungeons and hanging out in different towns c. 2000. You can still look around these virtual spaces today, but you'll have no idea how they were actually inhabited by players.
UO ruined other MMOs for me, it allowed too much freedom. In the early days, before trammel/felucca split you could attack anyone and take their gear. It really felt like actions had permanence, and you had an effect in the world.
I think most people look back fondly on UO who played it in its prime, but I don't know whether the state of things today would allow something even close to capturing that feeling.
When WoW came out it felt like the game was some sort of theme park rather than an actual secondary world. I couldn't bring myself to get invested in it like I was with UO.
Funcom's Anarchy Online just had it's 20th anniversary and feels the same way. It's easy to log back in and see the virtual world, but without players inhabiting the space it's missing the context that really caused these virtual spaces to be so significant in my, and I assume many other's, memories.
