Metroid Prime, originally released for the GameCube in 2002, is 15 years old. That may be hard to believe, as Retro's adventure game / first-person shooter hybrid still looks great, sounds great, and plays wonderfully well.
Metroid fans were nervous when word first came in that the franchise was going 3D – and being handed off to a Texas-based studio no-one had heard of, besides. It's a credit to Retro that Metroid Prime is still regarded as one of the best entries in the series.
It also speaks of Retro's penchant for care and detail that people are still marvelling over the small but lovely design choices in Metroid Prime. In a NeoGAF thread celebrating Metroid Prime's 15th anniversary, a user named Mousnis points out that if you use the X-Ray Visor and look at Samus' arm while she changes weapons, you can see her make the appropriate gestures with her fingers.
If you missed that detail the first time around, don't worry; you're not the only one. The motion isn't easily spotted unless you're looking for it. It's a prime (!) example of how much Retro cared about the property it'd been entrusted with.
It's also not the only instance of impressive graphical detail in Metroid Prime. If you get caught in a bright flash – after shooting a wall up-close, for instance – you can catch a glimpse of Samus' eyes reflected in her visor. Moreover, if you quickly turn around while the flash lingers, you can see her eyes move with the motion.
That tiny "extra" is impressive by today's standards. It was almost unthinkable fifteen years ago, but Retro pulled it off with ease.
It's a shame the future of the Metroid franchise is up in the air. Metroid Prime: Federation Force went over like a brick balloon, and if Nintendo has any plans for Metroid on the Switch, it's not talking.