As an ex-gamer, I have experienced a very wide range of attitudes coming from fellow gamers.
Now, the predominant attitudes that board gamers display are friendliness, competitive concentration, and hubris. These are not bad things. In fact, chess has been used to help people learn how to attain a deeply focused mindset. As I stated earlier, social games (that involve face-to-face interaction) are a great way to make friends!
Online gaming is a different beast altogether. There are friendly online gamers, there are rude ones, there are old ones, there are young ones. Some online games tend to draw a certain type of gamer, let's call them the douchebag (warning: language). Usually these are action games, something where violence is inherently part of the game. The more "hardcore" the game, the nastier the gamers can get. Their anonymity gives them a sense of empowerment and immunity to social norms. They feel they are entitled to be better, and that if they fail it is not their fault. I will admit, I have fallen for this a few times in the past. In fact, I stopped playing some games because they made me too angry. But something I never have and never will do is turn around and insult my fellow gamers. "Griefing," profanity, and pejorative language have always been a major issue on the XBox, for instance, which tends to have a higher percentage of these kinds of games than other consoles. But don't get me wrong, it is present on every game system. The best things to do when you find someone like this is to report them, ignore them, and then move to a new server/game. Don't stoop to their level.
There is also a sense of entitlement in MMOs. Griefing (doing whatever you can to annoy another player, from cursing at them to blocking their way to killing lower level characters to cheating/hacking) has had a rich history in just about every MMO out there. There are some exceptions. In general, the older the audience, the fewer douchebags there are. Lord of the Rings Online has a fairly mature audience and a very low level of griefing. Games themselves often try to reduce griefers through regulations and updates or reduce the ways in which they can grief. For instance, if you have been in an epic battle with a major boss, and then I run in at the last second and deal a few blows, some games would award all of the experience points to the person who dealt the final blow (called kill-stealing). But this is largely a thing of the past. LotRo awards experience points to the party that attacked first. City of Heroes used to award points to everyone who helped bring it down. It is, after all, about cooperation and not competition.
Something I have noticed, however, is that the kind of game makes a difference. City of Heroes was a very special game. It became family-oriented (many times I fought alongside kids as young as 6). The purpose was to stop the obvious bad guys, so those who played it often wanted to BE heroes. There were zones designated for cooperative play between Heroes and Villains, and zones designated as PvP (player versus player) zones. which were very carefully regulated. One of my fondest memories was of my brute (a villain) meeting a tank (hero) in a PvP zone and, after a prolonged fight, decided we would rather talk character creation and the like than just duke it out. If you ran into someone griefing or abusing the game in some way, the devs arrived promptly and took care of the situation. There were a few cases of griefing, particularly in the beginning, but the community started to change and soon became just that, a community. Players would spend hours in the Pocket Zone (a dance club) roleplaying and talking and having fun. Forums were very active. People helped each other all the time. We never let things get boring. Player -generated content was strong and had big names contributing. Games where actual roleplaying takes place tend to be friendlier.
Now, City of Heroes is dead. NCSoft decided that it would make more money killing the game (I believe they needed to do it for a tax break) than keeping it up and running (and it was a lucrative game that had just announced a new major update). They didn't tell their employees until the day they announced it to the world, and did so by handing them pink slips. They lied about "exhausting" all their opportunities to sell the game (it was discovered that many people state-side wanted to buy it, had the money, made offers, and were outright rejected without any discourse). They told players to try their new game, Blade and Soul (rated M for Mature due to graphic violence and gratuitous T&A). They ignored their audience, and as such have taken a HUGE hit to their bottom line. Whenever I see an ad for an NCSoft game before a movie, I stand up in the theater and decry their poor business practices. City of Heroes/Villains isn't the only game they have purchased and then killed to the sounds of angry player protests. But all is not lost.
The Phoenix Project came out of the ashes of City of Heroes and decided to start designing a game for the community, a "spiritual successor" to City of Heroes. The more time they have to work on the game, the better they get at it and the more details emerge. It is not run by a massive corporation, but rather fans and volunteers. This game, City of Titans, is starting to look promising. They have, in fact, begun a Kickstarter campaign to fund the project, and it is wildly successful. As of this writing, it has 27 days to go and has already raised $311,000+ from over 2,000 backers. Its goal is just 320k. This is a game I would like to get behind. I just don't know if I have the time.