Some people like the idea of being a mage in a game because they want to be Gandalf, Merlin, or any number of horrible fantasy pulp wizards that come to mind.  However, they ignore the literary role of the wizard in these books (except for the really horrible ones).  Gandalf used magic maybe a total of what, 4 times during Lord of the Rings?  Merlin barely used any at all in any iteration of the Arthur legends.  They did not run around tossing fireballs at everything that came their way.

The literary mage is often more plot device than protagonist.  There are a tiny handful of them in the world, and although everyone somehow knows that wizards are insanely powerful and are not good targets for a random mugging, the wizards don’t just run out and take over the world with their powers.  Generally, the literary wizard is a source of bizarre arcane knowledge, moral and ethical guidance, and the occasional ass-saving spell.  Yet because of the Grandfather Clause of Stupidity and the lack of imagination on the part of the average gamer, almost all player character RPG mages are just fighters in different clothing, using magic missiles instead of arrows, warding spells instead of armor, and summoned daemons instead of hired mercenaries.  Ho hum.

The literary mage, unfortunately, is not a very good model for any but the most hard-core roleplayer to choose as an avatar.  People have ever-shortening attention spans, and are not entranced by the idea of subscribing to a game so that their wizard can spend all his time in the library.  Given the fact that most so-called computer RPG’s are almost entirely about killing things, they want to be out there killing things.  They also don’t want to hang around with a party of fighters who do all the killing, providing motherly ethical advice all the time and firing off one spell every week.  In order to cater to this class of mage player, computer RPG developers (and pen and paper RPG writers) have turned the mage from a bizarre mystical figure full of arcane wisdom to a lightning-lobbing siege engine.

Unfortunately, due to the precedent set by all RPG’s since the original Dungeons and Dragons, this is what everyone expects from the mage.  They want to be more powerful than everyone else on the planet, of course, but they conveniently forget that literary mages have strange restrictions placed on them.  They remember, for instance, that Gandalf can kill a mighty Balron single-handedly, but they ignore the fact that he was not allowed to harm lesser creatures like goblins, who were part of the "natural order."  They remember that Merlin was the secret power behind the throne of Camelot, but they forget that he really didn’t do all that much aside from facilitating destiny (furthering the plot).  Wanting every possible advantage and none of the drawbacks of a character type is part and parcel for the typical gamer, even more so for the computer gamer, since the computer is an abysmal tool for any concern outside powerleveling.  The result is the cookie cutter generic mage, the character that people will play if fireballs do more damage than arrows.

Is there any way to return the mage to his literary role in an MMORPG setting?  probably not at first glance.  The only ways to make the MMORPG mage more akin to the sagelike literary mage are:

• Make all mages NPC plot devices, no player mages.
• Impose insane restrictions on player mages, in which case nobody will want to play them.

There are some middle roads as well, but they also fail to be satisfactory to the typical fast food gamer mentality:

• Assign penalties to the use of any sort of major magic, as in paradox points a la White Wolf’s unplayable Mage pen and paper system
• Increase the need for lore and people who can research it, which is rendered useless by people who simply make "mage mules" to find out information that then gets posted on a message board
• Use the "like affects like" system utilized by some fantasy novelists, dictating that magical powers are only truly effective against magical entities

The last point may seem like it has some viability, but in practice it fails horribly.  Using like affects like, a mage would be able to comfortably beat monsters with magical abilities, but would not do very well against, say, a mundane barbarian.  The problem is that the no-magic fighter is better than the mage against primarily magical opponents because he himself isn’t affected by magic as strongly!  You can try to tweak this a lot to make it work, but the best case scenario effectively segregates your world’s hunting areas, i.e. mages go here, fighters go here, and now your world is effectively smaller for all players.  This also tends to lead to bad loot situations where a fighter may be well-suited to go through a small pack of goblins, but the daemon the mage is killing is going to have the cool loot.

In conclusion, unless you completely rule out player character mages in any uncontrolled environment like an MMORPG, you will never approach an analogue to a heroic myth mage.  The only thing you can do is try to limit player accessibility to magical powers and then work on balancing the class types, so at least the mages will be relatively uncommon.