LOL buddy, pointless characters? No such thing i'm afraid. Barebones explenations incoming Metal Gear (1987)
Theme: The danger of nuclear weapons.
This is the easiest. The theme is expressed through the simple story of a secret agent infiltrating to stop a walking nuclear tank, Metal Gear. Nuclear weapons are a highly delimited theme stemming from Kojima's cultural background and interpretation of the bombings of Hiroshima and Nagasaki, as well as his feelings of insecurity during the Cold War, of which he has spoken in interviews. This theme carries throughout the entire series, but takes on a supportive role rather than a starring one.
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Metal Gear 2: Solid Snake (1990)
Theme: The possibility of adapting oneself when one's work becomes destructive.
This is where the games begin to get timeless, universal themes. Big Boss becomes a real character at this point, in order to challenge Snake's motivations. Snake returns to deal with the threat of a new Metal Gear, but in the process learns of Big Boss' plan to create perpetual, universal warfare as an end in itself. Big Boss argues that he's a warrior and therefore needs war, and claims Snake is no different. Snake denies it, saying that he fights only so long as is necessary to stop men like Big Boss. Big Boss fights and gives in. Snake fights, but can he give it up?
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Metal Gear Solid (1998)
Theme: The existence of free will despite genetic heritage.
Snake turns out to be a clone of Big Boss, and returns from retirement to stop his clone brother, Liquid Snake, from using a new Metal Gear to achieve Big Boss' dream. Again, the conflict is nearly identical on a superficial level. Liquid believes he's fated to be a warrior and so does exactly what Big Boss did, and Snake faces the same paradox of fighting to end war. All that isn't what's important, though. What's important is that this time the villain claims a specific form of determinism justifies his actions. Liquid says his genes force him to be a warrior, and, of course, that Snake is no different. Snake denies that genes eclipse free will. Snake is proven right in the end as he defeats Liquid and rides off into the sunset with a new, peaceful lease on life. Additionally, the final revelation that Snake was actually the inferior of the two clones serves the message that your genes don't determine your success in life. Again, you can see how cloning was brought in purely to serve the abstract point of the game. People complain that cloning was never mentioned anywhere in the first two games, and that things are retconned to make it work. They were, but the point is that the consistency of the concretes only matter within each individual game, not between them. How they connect from game to game is more or less a game itself. It's just to keep it all in one, beloved universe.
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Metal Gear Solid 2: Sons of Liberty (2001)
Theme: The existence of free will despite non-omniscience.
Raiden, a virtually-trained rookie agent, is sent on his first mission, ostensibly to rescue the president from a hostage crisis. An initial feeling that everything is somehow "off" bears out as the plot unravels the secret development of new Metal Gears, the control of the US by a secret society called The Patriots, and the manipulation of the events of the mission itself by that same secret society. By the end of the game, so many counteracting revelations have occurred that the player no longer knows what to believe, and Raiden doubts the very existence of his pregnant girlfriend. The Patriots reveal Raiden's entire mission to have been an elaborate experiment designed to test the hypothesis that people's actions can be determined by control of their access to information. The Patriots plan to use this method to speed up the evolution of the human species by censoring "junk" data, but Raiden argues that he has the right to judge for himself what's true, and that he has already done so despite the manipulations of The Patriots.
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Metal Gear Solid 3: Snake Eater (2004)
Theme: The existence of free will despite personal context.
About half a century before the rest of the games, Big Boss is sent on a mission to kill his beloved but traitorous mentor, The Boss. The Boss defects to the Soviet Union on the premise that allegiance to a country is invalid because countries change with the times. Big Boss maintains his loyalty and hunts down The Boss, killing her and proving his loyalty to the mission above all. A brilliant reversal then occurs, in which Big Boss discovers that The Boss' betrayal was a ruse all along, and her death freely chosen as a means of serving America's interests. Realizing that loyalty to the mission above personal desire has claimed the life of his great love, Big Boss rejects the choice to be free from the prejudices of personal desire and the times, and becomes the villain we all know. Except he doesn't, because the sequels had themes of their own that required Big Boss to twist this personal transformation into something it wasn't. Again, each game wreaks havoc on the others to serve its own ends.
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Metal Gear Solid: Portable Ops (2006)
Theme: The value of free will.
This was the first game not directed by Kojima, and the only one besides Revengeance so far. It was a game made by other people in order to get METAL GEAR onto the PSP. It did that, but basically as a rehash of elements from all the other games. It's definitely Metal Gear, but, to put it harshly, it's a pale imitation. It's a fine game, just not very original or interesting thematically. Six years after MGS3, Big Boss is framed for the hijacking of a nuclear tank. The actual culprit is his former special forces unit, led by a man named Gene. Big Boss must take them down in order to prove his innocence. Gene wants to create something like an age of warfare, but he'll do it dictatorially, and Big Boss thinks that's bad, hence the conflict. Additionally you can throw in some hints of the formation of The Patriots and echoes of the evil of negating people's will. The game's elements were a more generic, vaguer, less inspired way of reinforcing what had become the obsession of the series: free will.
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Metal Gear Solid 4: Guns of the Patriots (2008)
Theme: The limits of will.
Snake is old, and he's failed to stop the proliferation of war and Metal Gears. Big Boss' dream has seemingly been achieved by default, except the wars are controlled and fueled by The Patriots. Liquid plans to destroy The Patriots and create Big Boss' dream in full, and Snake is sent to stop him. Here is where what I said at the beginning becomes important. The keyword in this game is "legacy." It's all about how one's actions echo through time, and what effect one can have after one's death. That is why Big Boss vs. Zero over The Boss' intentions became important. It's a way of showcasing how The Boss influenced the world beyond her own lifetime, and what the limits of that influence are. The Boss' influence set the foundation for the entire plot. Big Boss' influence led directly to the motivation of the main villain. Zero's influence led directly to the rise of the current state of affairs against which the main villain is fighting. Liquid's influence led to the creation of the main villain. Emma's influence led to the virus that ultimately saves the day. The game illustrates in every detail that although a legacy can be powerful, it is up to the future to determine what becomes of it once its originator has died. Big Boss and Zero represent the betrayal of a legacy, while Snake represents its true heir, but the point is that The Boss had to leave it to the future, for better or worse. Liquid and Zero each represent in their own way the refusal to leave the future to the future, and the pretense at control beyond death. In the end, however, Liquid stands revealed as a fraud who died back at Shadow Moses, and Zero as a man who led the world to ruin out of fear of leaving his work to future mortals.
Metal Gear Solid: Peace Walker (2010)
Theme: The possibility of choosing peace in a hostile world.
Ten years after MGS3, Big Boss has his own mercenary company and is hired by Costa Rica to protect their peaceful country from the incursions of the CIA. A rogue CIA station chief plans to prove to the world that nuclear deterrence is the only way to avoid nuclear war, i.e., that commitment to hostility is the only path to peace. He has had an automatic nuclear retaliation system built, as well as an AI patterned on The Boss to control it. He plans to fake a nuclear attack on the United States, predicting that the government and military won't have the will to retaliate. The system, however, will retaliate with a live nuclear ICBM. This will prove that humans don't have it in them to do what it takes to achieve true peace, but that his system does, and the nuke it launches will be the last ever used by mankind. Snake fights to stop the plan, believing that using nukes to end nukes is wrong. In the end, all attempts fail to stop the launch, except The Boss AI itself refuses to ignite a war and commits suicide. This, the story says, was the true motivation of The Boss ten years ago. She realized she lived in a world in which hostilities were unavoidable, and so idealistically chose suicide over acceptance of the world as it is. I think Peace Walker is actually the most depressing of the games. All the others end with some kind of affirmation: free will does exist despite A, B or C, you can choose to change, you have to let things at some point as a natural consequence of the fact that people will have free will in the future just as you have free will now, etc. Peace Walker, though, explicitly lays bare the fact that what it wants is impossible, and that should you choose to strive for it anyway, you'll find it only in death.
Revengeance is not important. Read part 2