Last week, the video game world went all-in on nostalgia

In 2015, all the old video games are new again.

This year's annual video game industry trade show, E3, just ended last week. Sony's PlayStation keynote address, however, felt like it ended at some point in the late 1990s/early 2000s.

The biggest cheers were for the announcement of a remake of a game that originally launched for the PlayStation 1 back in 1997. Microsoft's hottest announcement? The ability to play your old Xbox 360 games on your new Xbox One console.

Nintendo, unsurprisingly, announced game after game starring characters that were created 20 to 30 years ago. 

This all felt particularly strange when juxtaposed with forward-looking virtual reality technology from those same companies: Microsoft made its "Minecraft" game series come to life (literally) with its HoloLens headset, and Sony announced a massive library of VR games heading to its PlayStation 4-based Project Morpheus headset. (Nintendo, for its part, isn't competing with emerging technology - Nintendo of America president Reggie Fils-Aime told Polygon last week, "based on what I've seen to date, it's not fun, and it's not social - it's just tech.")

The game industry's no newcomer to sequels, of course. One look at the Madden football series confirms this: there's a new Madden game every year, and there has been for over 20 years. Covering the game industry is a study in covering sequels.

But this year's E3 wasn't just heavy on sequels; it was heavy on nostalgia, and selling you games based on that nostalgia.

The 2015 Nintendo World Championships

The show unofficially started on Sunday (June 14th this year). The event that kicked things off? A throwback to a Nintendo event popularized by a 1989 film named "The Wizard," dubbed the "Nintendo World Championships." A variety of fans were flown to Los Angeles to compete in a series of Nintendo games against a variety of YouTube personalities in the world of gaming.

Though the event is a glorified promotional event for Nintendo games and products, it leans heavily on the nostalgia of Nintendo's heyday - the late 1980s/early 1990s, when the original NES system dominated the game market - to get fans excited. For example, Nintendo reps wore Nintendo Power shirts (the now-defunct, long-running magazine published by Nintendo), and they made game announcements for obscure classics finally making their way from Japan to the US. 

Games ranged from the hyper-current "Splatoon" to classics like "The Legend of Zelda" (the first one, which came out on NES in 1986). Like all things Nintendo, the Nintendo World Championships both promoted future games and made sure to remind fans that Nintendo's been doing the games thing for well over 30 years.

Welcome (back) to Hell

If Nintendo reviving its aging World Championships weren't enough nostalgia for one day, the company that makes "Doom" - yes, the "Doom" game you played in the mid-1990s - held a press conference the same evening to showcase the latest versions of franchises that started over 20 years ago. 

First up: "Doom." Here's the trailer that came out last week - warning that it's very graphic:

Pretty graphic, no? That's just the fourth iteration in a series that started back in 1993. The game's been in development, in some form, for the past eight years.

Old Xbox games, new hardware

Microsoft's Xbox press conference kicked off on Monday morning (June 15th), and firmly cemented the week's theme with a surprise announcement: the ability to play Xbox 360 games on the Xbox One. 

The announcement was huge news for the tens of millions of Xbox 360 owners, many of whom have yet to pick up Xbox One consoles yet. It was also an announcement of old games for a (basically) dead console coming to a new console. Great if you already own dozens of Xbox 360 games and are hankering to play them on a more powerful system, and great for Microsoft in vastly expanding its content library on the Xbox One! Not so great if you're looking for something new.

Playing PlayStation like its 1995

Nostalgiafest 2015 got even more serious that evening when Sony's PlayStation arm took the stage for its keynote. First up, the re-revealing of a game first announced in 2009, from a studio that found popularity on the PlayStation 2: "The Last Guardian." Though this game is new (and looks delightful), it enjoyed such a positive response on the back of games that its development team created in the early 2000s.

Hell, "The Last Guardian" started life back in 2007 for an entirely different console: the PlayStation 3. It looks like this:

From there, Sony hopped further backwards in time. A game named "Shenmue 3" was announced on-stage, and a Kickstarter was subsequently launched to support its production -- the Kickstarter campaign is already well over its goal, sitting at just over $3.5 million as of this writing.

For some context, the last "Shenmue" launched for the Sega Dreamcast and Microsoft's original Xbox. That was in 2001. 

Not to be outdone by an aging Sega-created franchise, Sony tripled down on nostalgia with an announcement fans have wanted since...well, since the game originally launched. The seminal Japanese role-playing game "Final Fantasy VII" is getting an official re-make, which caused the live audience to wildly roar with approval.

Sony actually built a social media campaign around its nostalgia-laced stage performance, dubbed "The List." Here's PlayStation VP of publisher and developer relations Adam Boyes introducing that campaign:

Nintendo loves Super Mario

Nintendo stopped having an official keynote presence at E3 several years ago, instead opting to host a "digital event" where the company streams a pre-recorded video presentation in place of a live stage show. Despite this innovation, the company stuck to its nostalgia-filled guns this year with a variety of game announcements that lean on its most popular franchises: Super Mario, Super Smash Bros., and Metroid, among others. 

And that was all before the show even started. In 2015, everything old is new again in the world of video games.