If you are looking to start a gaming collection (circulating, or just for in-house use) at your library, or if you just need a video game website to go to for personal use, I recommend GameSpot (*not to be confused with the store GameStop - even though I always get the two mixed up).
This is a great website for a range of people who know nothing about video games except that they want to start playing them, all the way to experts who think they know everything, but sometimes still need a little help from a walkthrough to beat the last level.
GameSpot features previews, reviews, and trailers for all platforms. They offer demos and patches for current games, gaming news and information about new releases, and a forums section to chat with other avid gamers, or if you're a newbie asking for advice. The site has a section for iPhone and other mobile games, which I haven't explored since I don't use my phone for games.
You can search for games by title or console, where each result will be a page about the game including an area to check prices at different stores, News & Features, the rating, and screenshots. If you are ever wondering if a game is multiplayer and can't tell from the summary, you can usually click on the picture of the game's box and click "Back", and it will show you the back of the box, where you can see the number of players. The page will also offer suggestions for similar games you might like, if you already know you like the game you have searched for.
My favorite feature on the site is a list of the top video games. This list can be viewed as a collective list of the top games out of all of the platforms, or broken down into whichever console you are looking for. There are three different scores for the rating: Critic Score, User Score, (they allow you to review the video games too, or save your numerical rating for your own reference), and GameSpot Score. To read more about how GameStop determines the score for their ratings, you can go here.