"No matter where you go, there you are...."
In order to understand the Wish spell, one needs to understand the roots and origin.
7th Level Magic User
A spell which alters reality past, present, or future, but only within limited bounds. It cannot create or bring any form of treasure, for example, and only a portion of a wish might actually occur. (See DUNGEONS AND DRAGONS, MONSTERS & TREASURE, page 33, Three Wishes.)
9th Level Magic User
The same spell as found in a Ring of Wishes (DUNGEONS AND DRAGONS, MONSTERS & TREASURE, page 33). Using a Wish Spell, however, requires so great a conjuration that the user will be unable to do anything further magically for 2-8 days.
Ring of Three Wishes (DUNGEONS AND DRAGONS, MONSTERS & TREASURE): As with any wishes, the wishes granted by the ring must be of limited power in order to maintain balance in the game. This requires the utmost discretion on the part of the referee. Typically, greedy characters will request more wishes, for example, as one of their wishes. The referee should then put that character into an endless closed time loop, moving him back to the time he first obtained the wish ring. Again, a wish for some powerful item could be fulfilled without benefit to the one wishing (“I wish for a Mirror of Life Trapping!”, and the referee then places the character inside one which is all his own!). Wishes that unfortunate adventures had never happened should be granted. Clues can be given when wishes for powerful items or great treasure are made.
Most of the spell instructs the DM on how to screw with overly greedy players, possibly a result of the kinds of players Gygax typically played with, considering how often that sort of advice is given throughout the game.
Note the debilitating effects of casting the spell.
We skip ahead to 2nd ed for our next historical pit stop:
Casting Time: Special
Area of Effect: Special
Saving Throw: Special
The Wish spell is a more potent version of a limited wish. If it is used to alter reality with respect to damage sustained by a party, to bring a dead creature to life, or to escape from a difficult situation by lifting the spellcaster (and his party) from one place to another, it will not cause the wizard any disability. Other forms of wishes, however, cause the spellcaster to weaken (-3 on Strength) and require 2d4 days of bed rest due to the stresses the wish places upon time, space, and his body. Regardless of what is wished for, the exact terminology of the wish spell is likely to be carried out. Casting a wish spell ages the caster five years.
This discretionary power of the DM is necessary in order to maintain game balance. As wishing another creature dead would be grossly unfair, for example, your DM might well advance the spellcaster to a future period in which the creature is no longer alive, effectively putting the wishing character out of the campaign.
Note again the penalties for casting the spell, and the monkey's paw advice to the DM.
Implicit in these descriptions are the implication that anything can be wished for... but the DM is supposed to make your wish not unfairly affect the campaign at the expense of the player character.
In 3rd ed, a list of safe options is given, and then one unsafe option, even though it does not have a bullet point:
You may try to use a wish to produce greater effects than these, but doing so is dangerous. (The wish may pervert your intent into a literal but undesirable fulfillment or only a partial fulfillment.)
In other words, even in 3rd ed you can wish for literally anything... but expect to suffer if you actually try it. Note the "Danger Will Robinson" clause.
Thus the scope of the Wish spell in 3rd ed is basically anything the player is willing to risk suffering the consequences for having wished for it.
It is interesting to note that in 4th ed wish is not a spell players can cast at all, and in 5th ed, some of the penalties for casting the spell are back.