This year marks the 25th anniversary of the Metroid series of games, and Nintendo is celebrating in muted style. Nintendo of America's official Twitter account reminded us to log into the 3DS e-shop to download the free version of Metroid Fusion we were promised as ambassadors, but that was it. Fans took to the cause with gusto, however, and a wave of fan-made art and musical projects have spread across the Internet.

Nintendo's lack of enthusiasm for one of its core franchises isn't surprising; Metroid has always been an odd duck among the company's games. Besides, Nintendo is busy worrying over the success, or lack thereof, for the 3DS and paving the way for the upcoming Wii U.

No new Metroid games have been announced, but the upside is that Metroid remains one of the few series that Nintendo has not beaten into the ground. That's just fine: the game's hero, Samus Aran, has always been a loner.

Her name is Samus Aran

The original Metroid, released in 1986 on the NES and making an immediate splash in the United States, was built on well-known influences. Every game stands on the shoulders of the titles that came before it, but Metroid took games of the time and mixed them together to create something new and amazing. The game had the platforming elements of the Mario series and the non-linear exploration aspect of Legend of Zelda. You had to explore the environment to unlock new weapons and abilities, which would then help you explore even further to fight the increasingly powerful enemies put in your path.

It wasn't a sunny game, and you sure as hell weren't fighting turtles or the cute little enemies from Legend of Zelda. The game made you feel alone in a hostile environment filled with native life forms that wanted nothing more than to feed on your corpse. The final encounter pitted Samus against a pulsating brain, but the real bad guys were always the Metroid life-forms themselves. It was clear the development team borrowed liberally from Ridley Scott's film Alien, down to the name of one of the game's boss characters, but the game's appropriation of the themes from the Alien series goes deeper than some faux-Giger designs.

Just as with Ripley in those films, Samus Aran's life became intimately linked with that of the Metroid life-forms. She fought them, and in the series' Game Boy debut she was tasked with hunting them down, but in Super Metroid the last remaining Metroid also saves her from defeat at the hands of Mother Brain. She can't escape them, nor they her. They both share many of the same characteristics: both are violent, capable survivors.

This is perhaps illustrated best in the triumphant Super Metroid, which is considered one of the best games ever made. "What's most impressive about the game is its atmosphere. The Super Nintendo may be woefully underpowered by today's standards, but that hasn't diminished the atmospheric nature of Super Metroid one bit," we wrote in our Masterpiece entry for Super Metroid. "The feeling of being alone on an alien world is incredibly powerful, and this has a lot to do with the game's dark and foreboding soundtrack."

That game added a map, allowing you to better plan your exploration, and it moved the Metroid story along, setting the stage for the most recent game, Metroid: Other M. Super Metroid may have been released near the end of the Super Nintendo's life cycle, but it still found an audience and helped to create the now-ubiquitous "Metroidvania" style of games that combine exploration with action and item collection. The game began with a countdown and a feverish escape, and it never let up until the game's surprising finale. The detailed and fully realized world make this a game that's easy to return to, even for modern gamers.

The Prime series of games took the Metroid world and turned it into something that looked like a first-person shooter. Fans were skeptical. The games remained true to what made Metroid so compelling, however, and they became hits as well. The game curved your view of the action at the edges, making it feel like you were inside the armor, looking out through the eyes of Samus Aran. If anything, this added to the game's claustrophobic feel, and gave you the sense of exploring even more effectively designed environments. You were still alone, you were still fighting the Metroids, and it still felt like an impossible job.

The series also found success on Nintendo's various portable systems, and although some of the games were more linear than others, there has yet to be a single "bad" Metroid. Heck, even the pinball game was good!

Does it matter that Samus Aran is a woman?

The moment that Aran removed her helmet to reveal blonde hair and female form in the first game was a shocker for gamers of the time, but since then her sex has become less of an issue. The fact that no one makes a big deal about Samus Aran being a woman is notable, as is the fact that she's a capable warrior and survivor both in and out of her armor. This changed with the release of Other M on the Nintendo Wii, with many critics annoyed at the decision to "humanize" the character, making her vulnerable and putting the fact she's not a man front and center when she deals with others.

Her existence as a woman never really needed to be explored in depth, and it worked better when simply presented to the gamer as the reality of the situation. There were some undertones of motherhood with her caring for the newborn Metroid from Metroid 2 on the original GameBoy, but again that worked better as an implicit piece of storytelling. Other M felt the need to continually beat you over the head with the fact of Aran's womanhood, and it was a weaker game for it.

The Metroid series contains some of the most influential games ever made. The non-linear gameplay that rewarded exploration and an OCD-like need to find secrets, the different weapons that were stronger or weaker against certain enemies while also changing the environments to allow you access to new areas, and even the realization that adventure games could work in a first-person view... Metroid changed the way we game. It may not be one of the most important games to Nintendo, but is that a bad thing? This isn't a character who needs to be trotted out every year with a new game.