Metroid Prime 2: Echoes (Metroid 6) was the second Metroid game for the Gamecube and continued the Metroid Prime series. The same first person perspective is back with a very similar HUD.
This game isn't quite up to the high standard the original set but is still a great game. The graphics are slightly better, but not by much. Gameplay is really the same (which means it is great!). Challenge is similar to original.
So... where does this game lose the .8 points that separates it from the original? Story and Fun Factor. The story is interesting and original but the game just doesn't have the great feel that Metroid 5 did (going to use numbers and saying Prime all the time can get confusing). Echoes just isn't on the same level as its predecessor.
This does not mean you shouldn't go get this great game. Play Prime first, then Prime 2. You'll know what I mean when you do.