To mark GameSpot’s Game of the Year 2015 series, throughout this week we will publish annual performance reviews of all home game platforms: Xbox One, PlayStation 4, Wii U, and PC.

Yesterday we examined the Wii U, which experienced a year of experimentation defined by mixed success. Today we move on to PC, a system with numerous experiments of its own, but an open nature more tailored to trying new things. Below you’ll find a collection of headline observations that defined the platform's performance and evolution in 2015, followed by a final verdict for the year.

A Great Year for Mods

If there’s one area the PC platform can call its own, it’s the realm of modding, where dedicated enthusiasts take something great, and make it better. And with a wide selection of massive, open-world games to choose from this year, it’s no surprise the modding community has put its creative hands to good use.

Because who doesn't want apocalyptic lightning storms in The Witcher 3: Wild Hunt? Why wouldn't you dress as Buzz Lightyear in Fallout 4? And why not add RPG skill trees to Grand Theft Auto V? Games may begin their lifespans as static experiences, but the flexibility of the the PC democratizes the editing process, allowing audiences to craft something new for the wider player base.

Modding tools aren't consigned to PC in the long run: CD Projekt Red has expressed interest in bringing Witcher 3 mods to other platforms, and Bethesda has an actual plan to do so early next year. But as of 2015, and the foreseeable future, the PC platform has the upper hand when it comes to eclectic modifications.

Steam Machines Launch (Sort Of)

In Valve's attempts to branch out from the traditional desktop PC, few are more pronounced than its Steam Machines. These PCs were designed to be scalable and modifiable, allowing a large number of options for users with varying preferences. And on Oct. 16, Valve released pre-order units to the public.

Each version of the Steam Machine comes with Valve's linux-based operating system SteamOS, as well as the new Steam Controller, but from there, the similarities dissipate. There are several options available on the Steam Store, with prices as assorted as their hardware: the cheapest box, the Alienware Steam Machine A, sells for $450 USD, while some of the more expensive models reach prices in the several thousands.

Valve's full Steam Machine experience has yet to materialize, with a lacking current lineup.

However, of the 14 original vendors Steam said would be shipping Steam Machines at launch, only three have products available on the Steam Store as of this writing. Various reports suggest SteamOS may not be ready to support very high-end PCs, leading to certain companies' launch delays. Furthermore, SteamOS only supports a small fraction of the games available on Steam. So while 2015 was purported to be the Steam Machine's inaugural year, the full experience Valve is promising has yet to materialize.

Then there's the Steam Controller itself. While the device does work with certain genres, such as turn-based strategy or third-person action, its touch pads falter when trying to emulate the thumbstick experience. This makes first-person shooters a slog to play, and when it comes to MOBAs, which usually require quick reaction times, the Steam Controller is no match.

The Steam Machine and Controller are the next of many steps in bringing the PC platform to living rooms, along with a variety of options for individual users. The complete assortment of Steam Machines may not be available at the moment; SteamOS has yet to support more of the games available on Steam; and Valve still has tweaks to make with its unique controller, but 2015 has undoubtedly made progress in the efforts to move the PC past its desktop origins.

VR Growth and GPU Support

Virtual reality has struggled in recent years to find footing as a viable way to experience video games. This is due largely in part to the current lack of an available retail headset. Because of this, developers have had trouble convincing the general public that VR is here to stay, facing hurdles such as vague price points or higher hardware requirements, and until recently, the big picture still seemed a little blurry.

But both Sony and Microsoft have made efforts to push VR farther into the public realm. Sony says it will have 10 titles ready for launch on its PS4 VR headset in 2016. Meanwhile, Microsoft has announced partnerships with both Oculus and Valve, suggesting it has no plans to ease back on VR development.

Much of VR's progress has been focused on the PC, though. The platform's flexibility allows developers to experiment with different hardware requirements, and utilize more powerful hardware than that found in the console space. In September, Oculus announced the "Oculus Ready" program, which comprises a line of PCs that will work with the Oculus Rift straight out of the box.

While console developers continue to work out new ways to support wider libraries of VR games, the PC platform can support VR in its early stages with higher-end graphics hardware. Take Nvidia's GeForce GTX 980 Ti GPU, for instance. This unit was designed to support GameWorks VR, a software development kit tailored for developers focusing on development in the VR field. Better hardware means less stutter and latency, and more support for better looking VR experiences.

If 2015 has shown anything, it's that VR is more than just a fad. Companies such as Nvidia, Valve, Sony, Microsoft, and Oculus are all committing more funds to research, development, and public relations for their respective VR efforts. And much of that progress has taken place on PC. The platform's flexibility and capacity for better hardware allows developers to experiment, and gradually implement, more advances in the VR field.

If 2015 has shown anything, it's that VR is gaining traction, and it's more than just a fad.

Windows 10 Xbox App on PC

With this year's launch of Windows 10, Microsoft also released its Xbox app on PC. For anyone who's used the Xbox One, the interface will look strikingly similar on PC: multi-colored, multi-sized preview boxes lined up in rectangular patterns across the screen. The Xbox app on PC also pulls your software library and friends list directly from the app's Xbox One version, in an effort to bridge the gap between platforms. You can even stream games from your Xbox One directly to your PC screen, bringing the games from Microsoft's flagship platform to your monitor.

However, not all of the app's features work as they should, showing problems with everything from streaming to availability in the Microsoft store. Most of the store's games are still mobile ports, as Microsoft has yet to integrate a fuller library on PC, and besides--most PC users already have a reliable place to buy games: the Steam Store.

A major point of the Xbox App on PC is to give Microsoft a bigger portion of PC game sales. And this area is already dominated by Valve's platform. The majority of PC users rely on Steam for buying and downloading games, and the lack of major titles Microsoft is offering to PC users is a problem. Then there's the basic design of the PC's Xbox app itself. Like its cousin on Xbox One, the app is laid out in multi-colored, multi-sized preview blocks arranged in rectangular patterns. But aesthetics notwithstanding, the app's actual functionality creates a barrier, even following November's update.

Although Microsoft's efforts to branch into the PC gaming space have undoubtedly began this year, the Xbox app on PC still has obstacles ahead of it. With further updates, a better PC game selection, and a better user interface, the publishing giant could gain footing on another platform. But as of now, the results have yet to show.

The International Tournament Sets a New Record

In recent months, eSports have gained traction among mainstream media circles: ESPN 2 broadcast Blizzard's Heroes of the Dorm event, a MOBA tournament that competed for viewers with the NBA and Major League Baseball. In October, Activision Blizzard also hired former ESPN and NFL Network president Steve Bornstein to help head up a new division dedicated to eSports.

But despite broadcast media's recent foray into competitive gaming, online streaming channels still draw the most gaming-oriented viewers--and 2015 was a record-setting year in this respect.

The PC platform continues to be a bastion for eSports communities.

The final prize pool, which Valve bolstered via sales of its interactive book called the Compendium, exceeded $18.5 million USD this year. The International 2014 prize pool was just above $10 million. For further comparison, this year's $18.5 prize pool doubles the total prizes of the Master's Golf Tournament, and almost doubles total Super Bowl winnings.

These numbers show the massive--and still growing--popularity of MOBAs, a genre largely housed on PC. But they also represent a momentous shift in the way we watch games, and how we share our experiences with others. Services such as Twitch allow us to stream games to people across the world, despite increasing focus on sharing capabilities for the PS4 and Xbox One, PC users still have the most ease of use in this area.

The Verdict

Like the PS4, Xbox One, and Wii U, the PC has been home to numerous experiments throughout 2015, with varying results. It's a bastion for VR growth, and it fosters a massive community for competitive gaming. However, like the other platforms, it has also struggled with new ideas, whether it be the Windows 10 Xbox App, or increased presence in the living room space.

But the PC platform is still growing. Its hardware changes. It's flexible. And that's one of its greatest strengths. The PC facilitates mod support, far better visuals, VR development, and thriving eSports communities. It also allows people to scale the final product to their budget needs. The PC remains a versatile platform, both for the people making games, and the people playing them.

Despite its slow start with several new ideas, the PC is a bastion for modding, VR growth, the eSports community, and users who want a flexible platform.

The Good The Bad Steadily increasing mod support.

Flexible hardware allows for VR advancements and user-tailored machines

Home to thriving eSports communities

Initial steps into the living room sphere Steam Machine lineup has yet to materialize

Windows 10 Xbox App remains disappointing

SteamOs only runs a fraction of all Steam games

Come back Monday, December 7, for part 1 of our coverage of the biggest news of 2015, and let us know what you think in the comments below!