Yeah, except for wizards written in novels for D&D/PF...
Or wizards directly inspired by those, for example, Pug from Raymond Feist's Riftwar saga is a D&D wizard.
I stand by the statement that at the time of his creation, Gandalf had no literary peer. A good argument could be made that Merlin is no more than 4th level - Merlin in the original stories almost never employs anything more powerful than Disguise Self and Alter Self. Certainly at most he is roughly the same level as Gandalf, with perhaps access to the Polymorph spells (on the assumption that some of his guises might not be mere tricks) suggesting a level or two higher. Gandalf at the time of his creation is one of the most powerful wizards ever penned.
Most of the wizards of antiquity were penned by people who believed magic was real. But these people were not stupid. They knew they lived in the real world and they knew what the real world was like. So they knew that real magic had to be fairly subtle, else it's effects would be more clearly seen. Magic was needed only to explain things that weren't explainable otherwise. The also knew that real people couldn't do magic, and so if a wizard was performing magic he was doing it by compact with some other being - a god, a demon, a spirit, the devil or such like. Often this compact was only available to those with special inhuman heritage. Truly powerful effects required some talisman of some sort - some bit of arcane technology they knew how to employ. Wizards of antiquity were generally limited to effects like changing shape, prophesy, curses, binding spirits, charming persons, and the occasional illusion. They were noted by their ability as tricksters and con artists - which makes sense if you consider it. Merlin is mostly a master of disguise that uses it to get the best of others. And in general, most of them could be thought of in D&D terms as clerics or shamans of some sort, since their magic was not arcane but divine - accessed by some relationship for some sort with a more powerful being who does things on their behalf. The wizards of antiquity by and large do nothing that a D&D wizard can't do by 6th or 7th level, especially if we allow them to own a few magic items.
Literary wizards generally followed in the footsteps of these mythic traditions. They were generally either villains in D&D terms of quite low level, pitted against ordinary humans, or else quest givers with power of plot but little active role in the story and no more display of power than perhaps the ability to whisk one off through a door to faerie.
Gandalf is something of a revelation, particularly because his inhuman nature is hidden from the reader. Gandalf does not rely on a bound spirit for his power. And Gandalf's abilities are comparatively not subtle at all. Gandalf is a master of fire, light, and shadow. He kills goblins with lightning bolts. He conjures fire to burn his enemies. He creates blinding flashes of light. He turns invisible. He can blast open doors and smash bridges. He exists in the transition from the wizard of historical belief with its bindings, pacts, and curses, to the largely non-occult wizard of modern consensus fantasy. He's the archaeopteryx of wizardry - half ground in the fairy tales of the past and half filled with the innovation of the future.
Gandalf + Mazirian is the D&D wizard, and from the D&D wizard comes pretty much every other wizard in modern culture. And, granting that they are interpreted as high level spells in D&D, it's worth noting that Mazirian can only cast 5 spells in a day, which makes him what level? Mazirian (and Vance generally) gives D&D many of its high level spells - Prismatic Spray for instance. Mazirian is also doing his magic in the far future - magic and technology are the same. This completes the creation of the non-occult arcane wizard of D&D whose is human but whose powers come entirely from within.
The irony of course for me is that now the D&D wizard is generally perceived as being too weak and too constrained. There is a strong continual push for the wizard to become a demigod, and then to leap over that to full blown godhood. The perceptions of what is appropriately wizardly grow in the same way that the powers of any comic book character with powers tend to grow over time - not merely faster than a speeding bullet, but faster than light; not merely able to leap a tall building in a single bound, but to fly at will, not merely stronger than a locomotive but able to move mountains, etc.
