IGDB.com is described as 'Next-gen website about video games, intended for both game consumers and video game professionals alike.. A comprehensive, growing database, IGDB is built to cover video games in extensive details, including history and other information about developers' and is a Review Website in the online services category. There are more than 50 alternatives to IGDB.com, not only websites but also apps for a variety of platforms, including iPhone, iPad, Android and Android Tablet apps. The best IGDB.com alternative is RAWG, which is free. Other great sites and apps similar to IGDB.com are Metacritic, MobyGames, Backloggd and The Visual Novel Database.
IGDB is all about the games data - Completionator is more about me and the games I own or wish to play.