As a gamer, I try to keep up with news in the gaming industry. So whenever a new game is announced, sometimes I'll watch the trailer and get excited. Only when the game is released I end up being disappointed. What happened between announcement and release that led to my disappointment? The answer, in short, is hype.
Hype usually starts with a few trailers or gameplay videos. Game companies regularly develop trailers for their games for the same reason film studios do, to get people excited. Why would a company show something in a trailer that may not be perfect? For that reason trailers, more often than not, do not show any gameplay. Maybe the game is not at a stage where that is appropriate, or maybe the developer knows that showing what the game is actually like may take away from the hype. Gameplay videos on the other hand almost never show what the player is doing. Some newer gameplay videos demonstrating motion controls do show the player but only because you may be watching the video only to know how the motion controls work. If a gamer would have trouble doing something, then chances are that will not be shown in a gameplay video, either purposely or accidentally.
As a new game's release date gets closer and closer, generally the gaming media will get a few chances to play it, maybe at a convention, or maybe with a pre-release edition. Their impressions are then generally posted on their respective websites. The fact is that with previews, unlike reviews, the previewer tries not to focus on the game's faults. This is usually because the game might not be done. However, sometimes the previewer just wants the game to be good. Sonic Colors, for example, looks like a good game, and every preview I've read has nothing bad to say about it, but gamers want another good Sonic game and may overlook faults without realizing it.
The misinformation commonly known as hype only serves the purpose of getting people excited for a game. There is nothing wrong with it, but you'll never know what a game is like until you play it for yourself. However, the differences between the hype and the actual game may lead to disappointment.