This is a guest post by @tladb which was originally a comment on my original World of Warcraft and EVE Online comparison.
The biggest difference between the two games is the role of the players. In essence WOW is a solo game with the ability to join up with other players. EVE absolutely depends on the players to make the game.
In an extreme case if you were the only player on a WOW server you could arguably still have an interesting time just doing the quests solo and exploring the world. (Sometimes it feels like this in less populated areas in Azeroth now.) In EVE this situation would be pointless.
WOW is much more directed than EVE is sand-boxed. Basically all your activities in WOW are scripted by Blizzard. In EVE it is the players that direct the activities to a much greater extent. This means that after a new EVE player has finished the introductory quests it is up to them to find a role in the game. In WOW the NPC's will often direct you to the next area for quests. This may be the hardest thing to come to deal with. Are you going to be a pirate, a pirate-hunter, a miner or an explorer or even a corporation director, etc. In EVE these are all possible, but the player has to decide and then work out how to apply those skills. Especially since many of the occupations depend on other people.
This emphasis on player interaction is the major theme within EVE. The economy depends on other players not only in buying and selling basic materials and quest trash but also in making available important weapons systems. In WOW to get the best gear you need to get it from the NPCs either from instance drops (going into dungeons and killing the same NPC again nd again and ..) or PVP grinds.
In EVE, the items are player-built. So if there is a popular item in EVE not only will that be available at a price but in the supply chain to provide that many EVE players could benefit. Even at a relatively early level you could be part of that chain. There is also the point that making and trading items in EVE is much more involved and and potentially more interesting in comparison to WOW.
In WOW player guilds are much more casual with the more limited focus of providing a pool of players for raiding instances. There are no player stations in WOW, no pirate guilds or guilds in WOW with a bigger concept than just loot-runs. A WOW equivalent of a training corp like Eve-Uni for example would be completely baffling. I think it could be argued that the large majority of your enjoyment in EVE is determined by the corporation you join.
One big shock in EVE to WOW players is that getting killed in EVE is more than the two minute inconvenience it is WOW. Your ship, which you spent hours, days or weeks to acquire is lost. There is the possibility that you may have lost weeks of skill training time if you have not kept up to date your clone. Death matters. This is seen as a positive aspect for EVE players, otherwise they would not be playing; but for a WOW player it's a major change.
WOW has more of a physical presence than EVE. The places you visit are more visual so that just wandering around in WOW is interesting. Wandering into Ironforge, the strangeness of Sillithus, the workshow in deadmines, entering Outlands, just riding through Nagrand, the Deathgate sequence to name a few.
Visually space in EVE is a bit bland, there are better NASA pictures, however in EVE the sights need to be created by the players themselves such as the large fleets battles (using my imagination here).
Physically in EVE you are a ship and this ship can change depending on what you need to do so there is really no "you" in EVE. While in WOW you and other players have a visually existence. Neither is better but it is a difference perspective.
WOW has a better mythology and characters. Thrall and Arthas are two characters which I think should be in the literature canon. To interact with those characters really adds to the game and it is something that EVE does not have. If you have played Warcraft and then WOW it feels a big deal meeting with Thrall for the first time or following the Arthas story in Lich King expansion.
WOW is a more convenient game to play. A couple of examples:
In WOW you can send anything by mail. Horses, pets, money, food, complete suit of armors, anything. In EVE you can send money but everything else needs to be physically transported. You can buy an item on the market from a distant station but you need to fly to that station to pick it up. And warping is star-to-star, not instant warp to trade hubs which you can get in WOW. This is by design and provides a more dynamic environment for players; but it's still more inconvenient from a WOW perspective.
In EVE there is no user interface API which allows player add-ons. This is arguably a weakness of EVE. External applications like EVEmon, to help training, or Eve Fitting Tool, ship fittings, would be in game in WOW. Entirely different users interfaces are possible in WOW and not in EVE. It would be interesting and beneficial to see what a mod community should do.
EVE and WOW are two very different games with different objectives and quite different ways to play so it is not a question of better but what can you enjoy doing.
The opinions shared here are those of its author and not necessarily mine. /CrazyKinux