One of the biggest disappointments coming out of E3 was the lack of what many people feel is a proper entry in Nintendo's Metroid series. Even Nintendo understands the complaints, but that doesn't mean we'll be getting the Metroid that everyone wants anytime soon. Thankfully, gamers no longer have to rely on Nintendo to scratch that itch. Over the years, there have been a number of great releases that have emulated Metroid's exploration-based gameplay in a variety of original ways. Here are some of the best non-Metroid, Metroid games that fans of Nintendo's series should add to their catalog.