These were the 12 highest-grossing games of 2018 on Steam, the biggest platform in PC gaming

"Warframe" by Digital Extremes

"Warframe" is a free-to-play online action game with a mix of mission-based objectives and open world gameplay. "Warframe" has been around since 2012, but the game has been experiencing a massive surge in popularity, thanks to ongoing support from developer Digital Extremes.

While the game is free, "Warframe" offers a wide selection of armor, weapons, and items that can bought up front with real-life cash. Dedicated players can buy the same items with currency they earn while playing the game.

"DOTA 2" by Valve

"DOTA 2" is a free-to-play game developed by Valve, the same company that owns and operates Steam. Originally a mod of "Warcraft III," "DOTA 2" has been around for more than a decade and helped create a brand-new genre of video game, the Multiplayer Online Battle Arena, or MOBA.

DOTA 2 features more than 100 playable characters and primarily earns revenue by selling cosmetic items for use in-game. This year, Valve also introduced Dota Plus, a monthly subscription that charges users for access to advanced statistics and exclusive features.

"Tom Clancy's Rainbow Six Siege" by Ubisoft Montreal

"Rainbow Six Siege" has been a shocking success in the very competitive market for PC first-person shooters. The "Rainbow Six" series of squad-based shooters dates back to the 90s, but "Siege" has shifted the franchise formula.

Players now choose from an ever-increasing roster of soldiers with special abilities called "operators." Ubisoft has been able to keep its player base invested in the game by releasing new operators regularly, and the cost of new operator packs helps the game stay sustainable as it enters its fourth year.

"The Elder Scrolls Online" by Bethesda Softworks

"The Elder Scrolls Online" is one of the few high-profile massively multiplayer online role-playing games left on the market. Building from the world established in single-player "Elder Scrolls" games like "Skyrim" and "Oblivion," the online game has introduced a fair amount of new content since its launch in 2014.

To raise revenue, "Elder Scrolls Online" offers a monthly subscription called ESO Plus that grants players access to the all past and future downloadable content. Players can also purchase in-game currency through Steam with real money.

"Assassin's Creed Odyssey" by Ubisoft

"Assassin's Creed Odyssey" is one of the few new releases to make Steam's highest-grossing list. The game is a traditional, single-player action-adventure game following up on last year's "Assassin's Creed: Origins."

"Odyssey" benefits from the open world and role-playing elements introduced to the franchise with "Origins," and makes excellent use of its historic setting in Ancient Greece.

"PlayerUnknown's Battlegrounds" by PUBG Corporation

Along with "Fortnite," "PlayerUnknown's Battlegrounds" is largely credited with inspiring the "battle royale" genre of shooting games. "PUBG" is currently the most popular game on Steam with more than one million concurrent players at peak times.

While the game itself is $30 on Steam, "PUBG" also sells a range of cosmetic items to customize your playable characters, including items inspired by movies like "Suicide Squad."

"Counter-strike Global Offensive" by Valve

"Counter-strike" is pretty much the father of the modern first-person shooter, providing inspiration for an entire generation of PC shooters to follow. The game started as a modification of Valve's "Half-Life," but has since spawned a legendary competitive community.

The latest game in the series, "Counter-strike: Global Offensive," has seen a number of major changes to make the game more sustainable and provide new incentives for the dedicated player base. Valve began introducing cosmetic weapons and other rewards to the game, and players created their own economy by selling and trading rare items for real-life cash.

The game's popularity as a competitive esport and the odd economy surrounding the game have helped "Counter-strike" continue increasing its playerbase years after its initial release. Currently, more than 300,000 people play it on a daily basis.

In December, Valve took a major step by making the game fully free-to-play.

"Monster Hunter World" by Capcom

Though the series has typically been developed for handheld gaming systems, "Monster Hunter World" is the first "Monster Hunter" game in nearly 10 years released for home consoles and PC. The result is a remarkably beautiful adventure that asks players to stand in awe of nature, even as they attempt to tame massive dragons and wild creatures.

"Monster Hunter" may not be a household name like "Super Mario" or "Tomb Raider," but the action role-playing series is one of the most popular video game franchises in Japan and has garnered a healthy fanbase around the world.

"Sid Meier’s Civilization VI" by 2K Games/Aspyr

Until you've spent 100 or more hours building your own nation, it might be tough to see the appeal of "Civilization VI." 2K Games has slowly been updating the game since its release in 2016; this year brought the first major expansion, "Rise and Fall," and the announcement of a second expansion, "Gathering Storm," due out in February 2019.

With two new expansions for sale and the game seeing discounts on Steam, 2018 was pretty much the perfect time to pick up "Civilization VI."

"Far Cry 5" by Ubisoft

While "Far Cry 5" was one of the best-selling new releases of 2018, it wasn't exactly the most impressive. The game takes place in the back country of Montana and pits the protagonist against a Christian cult.

Despite presenting a clear analog to America's renewed white supremacist movement in 2018, "Far Cry 5" offers little in the way of social commentary in favor of the usual run-and-gun exploration that the series is known for. Like Ubisoft's other titles, the game's sales are also buoyed by additional downloadable content.

"Rocket League" by Psyonix

"Rocket League" is one of the greatest small studio success stories you can find on Steam. Developer Psyonix started working on "Rocket League" in 2013 as a successor to its niche 2008 game, "Supersonic Acrobatic Rocket-Powered Battle-Cars."

The basic idea is soccer with flying cars, and it caught on quickly. "Rocket League" surpassed 40 million players worldwide in January 2018 and the game has established its own esports circuit.

Furthermore, by consistently introducing new vehicles, colors, and music, Psyonix has built a robust library of content for players to invest in over time.

"Grand Theft Auto V" by Rockstar Games

"Grand Theft Auto V" hit PC more than a year after it arrived on Xbox 360 and PlayStation 3, but the PC port remains one of the best-supported games on Steam. Rockstar has been consistently releasing new content for the the game's online modes and earns extra revenue through the sale of in-game currency.

"Grand Theft Auto V" earned an impressive milestone earlier this year, becoming just the third game to sell more than 100 million copies across multiple platforms.

All of these games are on sale now!

All 12 games in Steam's platinum earners category are on sale through January 3rd, along with the vast majority of the games in the top 100.

Be sure to check the Steam Winter Sale for last chance deals on hundreds of games, and check out our list of the best games of 2018.