There is a large blogosphere where there are many gamers who love Video Games and often publish reviews for new or recently released video games. Websites where you can purchase video games also often have reviews.
One can find online video games rankings on video game review sites, such as IGN. Also, online retailers such as Amazon keep track of rankings as well.
There are many video game sites/blogs that review games for free. Some examples are www.ign.com, www.metacritic.com and www.gamestop.com. There are also many blogs that have actual people review games on a forum and have their review critiqued.
Most video games have a Wikipedia article that will list the genre of the game in the description box. Other sites that review games also have genre information. Some of the most popular are Game Informer, IGN, and the Xbox 360 website.
Speed runs of NES video games can be viewed on sites that review video games. The larger, more popular sites will have video to allow players to view the game before purchasing.
EB Games
Every video game has a rating on it. This will be very helpful when you are deciding if a video game is right for your teen or not. You can always go to gamestop.com too look at video games and they will have a desripction on the game.
VGP video game plus
Have you ever heard of video game exchange? It sell hundreds of old video games!
Game stores buy their video games from the video game manufacturer's company.
One can find a demo of recent Halo Games on the Xbox website as well as in supermarkets that have a video game section. Many video game stores such as Game Stop also offer demos of recent games inside the store.
One can find a walkthrough for the Prince of Persia video game online or in video game guide books. Websites such as IGN have guides and walkthroughs for many games including this one.
To find reviews online for games on the Sony PlayStation Portable, one could try one of the many game review websites. Examples include IGN, Gamespot and PSXtreme.