My all-time favorite video game, Echoes takes everything great about Metroid Prime and amps it up! As opposed to the isolated, sometimes almost bleak feel to the previous game, Echoes's atmosphere is more open and simultaneously darker. The actual gameplay hasn't changed too much, but the addition of various characters, backgrounds, and a parallel universe adds so much more to it. The puzzles have a very unique feel, as well, with the aspect of having to travel back and forth between the "Dark" and "Light" worlds. And let's not forget that this has two of the greatest locations in any video game: Torvus bog and Sanctuary Fortress. Definitely one of the most underrated games out there, even with it's positive reception.