I played EQ for 5 years and worked for Sony as a "guide," or online customer service, for 3 years. It is most definitely addictive. Basically (unless you're a real hard-core gamer with no job who can play 24-7), it takes the average person with a 9 to 5 job about a year to level a character from 1 to 70. Then you have to have good gear, so that you can join a good guild that does cool stuff like go to the elemental planes. To get the good gear, you need money; this involves a lot of "grinding," or killing the same NPC's over and over, to get exp and money. Then you can buy the piece of "uber" gear you were wanting (or that your guild was telling you you needed), and then there's something else you want/need.
Basically you want to join a good guild that's at the top or on the way up, and ideally stay with that guild, form bonds with other players, form family groups that hunt together all of the time, and go to the interesting places that not everyone in the game gets to see. In order to do that, you need max exp level, plus as many "advanced" points (AA's) as possible (and I think the cap for those is somewhere around 500) as possible, plus the best gear available (and often you need a guild to help you get the gear you want/need).
When you're in a guild, there's a lot of pressure to be online a lot, especially if you're in an elemental guild, and especially if you play a much-needed class such as a cleric, druid, or enchanter. I played a shaman and a cleric, and I felt a lot of pressure to play so that my guild could advance. You make many friends, and some of the relationships can be very intense, if you let them. My boyfriend actually left me for a woman he met in EverQuest (and they later married and had a child, yay).
It's hard to describe the environment. Many people continue to play so that they can see the "uber end game," and Sony keeps bringing out new content so that these power gamers can see new things and will keep paying their money to play. Others continue to play because of the bonds they've formed with other people within the game, and the friendships that they can't maintain out of game. I don't play any more, because I got sick of the "log in every night and grind exp" or "you have to be online on a Saturday night so we can go kill xx NPC, we can't do it without you."
Many of the EQ players that stayed with the game for so long, and were/are so addicted, began characters in 1999 or 2000 and took years to develop the characters. Nowadays, you can level within a year easily, in much less time if you have high level friends who help you with gear and buffs (helpful spells), but in the early beginnings of the game, everyone was learning everything for the first time; zones were brand new and dangerous to explore, and it took quite a long time to get the gear, money, and exp levels that eventually led to well-rounded, excellent characters with histories that the players enjoyed having. Many people don't want to give something up that it took 5 years to create and build.
I've tried almost every other game that's come out: World of Warcraft, EQ 2, and Guild Wars. They all have their good points: EQ 2 lets you be any race/class combo, by far the most varied of choices in character creation that I've seen (gnome monk?), but the graphics bog down even the higher-end machines; World of Warcraft (WoW) has an excellent questing system, little lag on less populated servers, and good graphics that don't bog down older machines, but there's a very limited selection of race/class combos; Guild Wars has the same type of quest system as WoW, but you can only be human, and there's only 4 primary professions (although you can be a combination of 2 of the 4).
Essentially, it's very difficult in today's online MMORPG world to begin a completely new game without have friends beginning and playing with you; in each game I've tried since leaving EQ, I've searched for people to play with and couldn't find anyone, that wasn't already playing with real life friends or friends from another game. I think that's one big reason that other games don't have the popularity of EQ; people stay with EQ because it's what they know, where their characters are "uber," and where their friends are.
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