Warcraft does everything as well as other mmo's in my opinion,
Heres my opinions.
PVE:
EQ1. Not even joking here. The raid game in EQ1 is unrivaled. It is /the/ premier raiding MMO, and it's been that way for ages. For standard leveling, there's so many options and content it's insane. There's so much depth and stuff to get your teeth into, I couldn't possibly list it all. 15 expansions.
15.
PvP:
Has to be UO. For anyone serious about pvp (in other words, people who take reward from the conflicts, not the shinies). EVE is also worth mentioning here. For anyone not serious, pick any other MMO, doesnt even matter. Killing a dragon, while fending off a guild thats attacking you - that's pvp.
Crafting:
Umm, dunno, don't do a lot of it. EQ2's crafting system I liked. WoW's is lame beyond belief, but not as bad as EQ1's.
Classes:
Vanguard. WoW is a close second though.
Community:
LOTRO, no question. Helpful and friendly. WoW has the worst community of any mmo I've ever played. Ignorant, rude and self-centred to the extreme.
Dungeons:
EQ1 again. Really complex and exciting dungeons, lots of risks and rewards.
Loot:
Have to give it to EQ1. Lots of cool stuff, some of it overpowered which makes it more fun. Clickies, such as insta-cast speed buffs, illusion masks, levitation rings, etc etc etc.
Getting a group at all levels:
Pretty important. Gotta be WoW here, though I've had no problems in LOTRO either. YMMV.
Housing:
EQ2. And the subject of housing is more important than most realise. Guild halls are just fantastic, as is filling them with interesting loot rewards, such as crafting benches, statues of dragons, pianos that play music, beer barrels that get you drunk, and of course a meeting point for your guild. Honestly, if you ever ventured into a lvl 60 guild house in EQ2 you'd be sold (as well as players having levels, guilds have levels too - the higher lvl your guild is, the more status and rewards you receive -- which in itself is a genius idea).
Lots, and lots, and lots of other stuff.
Can you see how "the best mmo" isn't a straight cut answer?