The Tome of Knowledge
Want to know how far along you are in a certain zone's storyline (and the rewards for each stage)? Open the Tome. How many high elf archmagi players you've killed? Tome. What's the deal with that big spider in the cave? You guessed it, look in the Tome.
From lore details to player stats, the Tome tracked everything. In addition, you gained stuff for completing things outlined in the Tome - titles, achievements, items, and even some special abilities. Being that WAR released around the same time as Wrath of the Lich King, it's arguable that WoW's achievement system came first... but it still doesn't hold the amount of information that the Tome of Knowledge had.
Each major zone had at least one public quest, and in most cases it culminated with some type of boss fight. The first one located in the Orc & Goblin v. Dwarf starting zone involved the coercing of a giant to help break through an enemy location. The orcs and goblins decide to enlist in the giant's formidable strength by capitalizing on his love of brew. For the Destruction side, the event went something like clear the trash Order NPCs, steal some beer barrels, then lure the giant to the dwarf fortress to help smash it. If you played Order, the objectives were to kill waves of attacking Destruction NPCs, then deal with their big ally in an explosive finale!
If I remember correctly, these were separate events in single-faction PvE-only areas... but there were also public quests in RvR spots as well. I recall the next zone (or perhaps farther along the same zone) including a mountain pass with a public quest for both factions in the same location. Players raced to forward their faction's public quest while fighting off enemy players attempting to do the same! It was EPIC.
Several years later, RIFT, EverQuest Next, and a number of other titles would build upon the public quest idea to create dynamic events and large, multi-stage quests that can run anywhere from hours to months for an entire server to complete.
The Dangers of City Life
When I say every major zone had a public quest, that included the capital cities as well. You could be walking the streets of the Order capital, and find a greater demon of Nurgle as you turned the corner.
This was the finale to a public quest in the city, unlocked by players completing the previous parts of the quest. I recall this happening on several occasions when I played, running for my lowbie life as a plague boss lurked the city streets! It really added to the atmosphere of the game as a reminder that even in town, you weren't entirely safe.
This was true for both Order and Destruction's cities. Wander down an abandoned alley, and you might get jumped by skaven. Perhaps you decide to get nosy and see what's going on at the Khorne training grounds - you'll probably be attacked by berserkers and Chaos hounds. Just look at that place and tell me anywhere there seems remotely safe.
The Destruction capital also had an arena where you could test your might against the servants of Chaos. I remember finding several quests that led me to that pit, where it was pretty much everyone for themselves (think Gurubashi Arena, but with big nasty NPC monsters to fight in addition to other players).
I'm not sure if any MMO since has added this element of danger to cities (perhaps AoC? I haven't played it but it sounds possible there), and I doubt we'll ever see anything like this again for a good while. Blizzard has attempted this several times now as an introduction to their next WoW expansion (Scourge raids pre-WotLK, Deathwing attacks pre-Cata), and players mostly whined about how their bank mules got killed while running to the auction house. *rolleyes*
I have much more to talk about concerning the best parts of Warhammer Online, but this post is already long enough. Join me for a second installment where I'll focus more on the PvP/RvR aspect of the game.