Fidel Castro is not a happy chap. Cuba's state-run media has launched a fierce attack on a new video game in which the object is to assassinate this leader of one of the last redoubts of Communism before the fall of the Wall. It is not just any old video game. Black Ops raked in $360m in a single day when it was launched in North America and the UK last week. It is the latest in the series of Call of Duty blast'em console games. The last, Modern Warfare 2, was the biggest grossing video game last year; some 22 million units were sold by an industry that now dwarfs Hollywood.

Until now, the six games in the series have concentrated on the Second World War as their background, with a couple of forays into a more anonymous contemporary locale. But this latest moves to a Cold War setting, with gamers being set a first mission of assassinating Castro on the eve of the 1962 Bay of Pigs missile crisis, the moment when the world came as close as it ever has to mutually assured destruction.

Havana is not amused. In real life, the CIA and Cuban exiles are said to have tried to bump off the grand old man no fewer than 638 times. Having failed, they are resorting to virtual reality, the Cuban news site has complained. To add insult to infamy at the end of the game's single player mode, a special Zombie level is unlocked in which presidents John F Kennedy and Richard Nixon wield machine guns to save the Pentagon from the otherworldly threat.

We are clearly running out of enemies with which to satisfy the blood lust of the game manufacturers. In recent times we have already had controversy after the last version of Medal of Honor let players take on the role of Taliban fighters killing Nato troops in Afghanistan. (The Californian manufacturers removed the option after the game was banned from US military bases.) Then there is a game called Muslim Massacre, in which players become a US soldier on a mission to "wipe out the Muslim race", progressing through various levels where they take on Osama bin Laden, Mohammed and, finally, Allah. In another, players take on the roles of terrorists in a civilian airport shoot-up. Clearly no one went broke underestimating the bad taste of the gaming public.

Any adversary will do. We are, like the omnipotent state in Orwell's 1984, permanently on a war footing; only the name of the enemy need change in our black-and-white view of the world – and nothing is much more black and white than going to war. Perhaps the reason these games sell better in the US and UK than elsewhere is because our political and judicial systems are intensively more adversarial than many outside the Anglo-Saxon world. The Cubans are clearly mystified. Games like this do not only heighten diplomatic tension by glorifying assassination; they also stimulate "sociopathic attitudes in North American children and adolescents".

The classic riposte to that is that this is only a game. The point of a game is that it is a safe simulation of reality in which we discover by trial and error. The reason that play is primarily the province of children is that they have a lot of discovering of the world to do. A game is a place in which you learn without being paralysed by the fear of making a mistake. A war game for a boy is a donning of the toga virilis. It is a place in which he can behave irresponsibly without real consequences. It is a fantasy world in which an individual can test aims or desires that are unsafe in everyday life.

Fantasy is helpful, because it offers an escape from the choices and tensions of reality. It is more than the suspension of disbelief that art requires. Like playing a musical instrument, it can be so absorbing it excludes other levels of perception. Psychoanalysts see it as a defence mechanism. When we fantasise about humiliating the school or office bully we are, temporarily, at any rate, reclaiming control. Freud thought it was even more enriching than that; human beings, he averred, "cannot subsist on the scanty satisfaction which they can extort from reality".

Fantasy is a liberation, because it brings together worlds which are at once both strange and familiar. The Archbishop of Canterbury has written interestingly of how such play is essential to learning. Talking irresponsibly, as he calls it, creates a new space within which children learn how the real world may be negotiated. Rowan Williams cites Alan Garner's book The Moon of Gomrath, in which elves fight with bows and arrows, not hand to hand with swords.

Reading that, a child learns that it is easier to kill at a distance, when you can't see into the eyes of your victim. They understand something about "the difference between knowing you're killing a specific person and indiscriminate slaughter". And the theologian saw that, long before the endless shooting, maiming, eviscerating and killing (press the right control to garrotte) of the latest Call of Duty game.

The point of fantasy – whether it involves elves or animals behaving like humans do – is that a child returns to everyday reality with new insights about acts, consequences and implications which have been learned in the course of the story.

One of the significant developments in modern gaming has been the age of those who do it. Today in the United States, and probably here too, 95 per cent of 12 to 14-year-olds play video games. A decade ago they grew out of them. But now, the statistics show young adults are returning to gaming, if they ever leave it, when they get their first jobs and can afford the latest versions of the technology. In Britain, surveys suggest that video games are now played by 32 per cent of adults. One in five women plays.

Is the learning process continuing? Or is it simply an escape from quotidian reality? In direct terms there is not much harm in that; despite the massive surge in video gaming in the US, violence among young people there is at its lowest level in 40 years. The anxiety is that, in some cases, fantasy can become a model for reality, a malign and only half-understood substitute for the real world.

The danger is that the narrative which some games inculcate is banal and simplistic. In one sense that is nothing new. It is there in the familiar Hollywood vengeance movie – which grows from a literary tradition that can be traced back to the revengers' tragedies of Jacobean drama. But gamers' fantasies of retribution are interactive. They are not spectators in search of catharsis; they are proactive initiators. There is no knowing whether that difference will take participants to a different place. But what is clear is that imagination, like language, can be corrupted, coarsened or cheapened. And that is good for none of us.

Last week afforded a backstop of exquisite irony. Men armed with handguns held up a store in Baltimore, making off with all its copies of Black Ops, on the eve of its release. In such ways, fantasy bleeds into reality.