Many of the advice columns I have seen on how to run a good role-playing game have said what to do about a troublesome player. For this purpose the GM's ultimate authority is usually hauled into play - what he says goes, and players should keep any out of game objections just that - out of the game.
Of course this isn't always terribly helpful advice. Its one thing for a novice GM to be told that he is right and his possibly vastly more experienced players are wrong, but quite another for people to feel that way. Players in this situation are exhorted to be as supportive as possible, ignoring or smoothing over anything that might be considered, with hindsight, to be a mistake. In theory this means accepting his judgement but more often it means tolerating it.
When playing a fantasy or science fiction game this is less of a problem - the society, setting, and even the laws of physics may be far different from what we are used to - so clashes with realism are slight or non-existence. However, more and more people are using modern-day settings, and thus involves making judgement calls about a world that is all too similar to our own.
In this situation it is pointless to tell people that that GMs judgement is final - people aren't going to accept that a crossbow to the head cause bruising damage or that a well aimed pistol shot is more destructive than a light anti-tank weapon. Should a creature from the NetherRealms(tm) cause someone to feel nervous, or die of a heart attack on the spot? Would extreme terror cause someone to run away or crumple into a helpless ball? How likely is cabinet minister to take bribes? Does it matter what party they are from? None of these have a right answer, but people can have strong feelings about them. A modern day game starts having judgement calls that interfere with how people see real life.
It becomes apparent that the GM does not, in fact, create the world in which the game is set. Everyone does. Just as the GM is trying hard to create a believable world so too the characters are trying hard to accept it; to have their characters act in that world as though they were there. This holds as well for unrealistic games as for realistic ones. Captain Lantern-Jaw may be impossibly larger than life, but then so is world he inhabits and both GM and Player must avoid bursting the bubble.
In the end it comes down to trust. The GM's decision is final, but only if the players trust him will that really become authority. It isn't hard to spot games where trust has broken down. See a game where the players are obsessed with well defined powers and abilities rather than backgrounds or other ref-dependent advantages, or where the players plans are only revealed to the GM when absolutely necessary - these are games in which trust has broken down. Similarly, if a GM creates a world in which the players are essentially spectators, involved but ultimately powerless in the face of important events or characters, then he does not trust the players. The game will slowly but inevitably fall apart as it is being played by only a single person - the GM himself.
I'm not about to suggest that the games be run by a vote of all participants, nor that the GM shouldn't make and enforce his judgement calls. What needs to borne in mind is that both the players and GM have a common interest in making a game work.
So what to do? As GM, try to listen to players. What they actually say is less important than the type of things they are saying. If they talk about style, plot etc. then you need not worry. They aren't the ones running the game. If multiple players complain that they can't seem to accomplish anything, then its time to change something. Whether you think they are being feeble or not is immaterial - you aren't a player and your opinion is unimportant.
Similarly, as a player, keep your out of game comments out of game. If your character is being killed unfairly then its better to complain after they're dead. Dramatic tension or positive game play will be lost through argument. Even if you can successfully reverse the GM's decision, the game and hence your character might never recover. If there is a long term problem, then mention it between sessions. If ignored, discuss with the other players and try again. Above all, try to co-operate with the game. Your GM has the right to expect you to at least try to participate with the plot. Don't play characters that always try to ignore everything and go home, or kill anything on sight.
In the case of serious trouble, with no reasonable solution in sight, then try putting the problem back into the game. If you are tired of being overawed by a succession of overpowered GM characters, then its likely your character would be too. Role play it! A character might pick up an irrational dislike of being ordered about, or become entirely too casual around important people. If magic is being employed to keep you respectful then your character would resent just as much as you do. It might result in an overpowering fear of being enchanted/beguiled/dominated or it might provoke you into a terrible frenzy. If you feel your character is being bullied once too often, then stand and fight for a change. Your character might not survive against the latest awesomely powerful whatever, but that isn't really your problem anymore. Besides which characters are often less clued up than players about their chances. If nothing else, impossible odds are the stuff of legend.
This technique is known as "the forces of anti-plot", and should not be misused. The idea is not to disrupt the game, but to disrupt your place within it - to make explicit the problems that are preventing you from enjoying yourself. The worst that could happen is that your character is eliminated by a vengeful GM, freeing you from a game that that is going down the tubes. The best is that the other players will do likewise - and the GM will be confronted with the conflict in a way he can't ignore. As long as you don't actively try to disrupt, and of course you keep in character, then your conscience is clear.
The game is created by the GM and by the players. The GM's decision is final, but the Players are still more important than the plot.