NEW YORK (TheStreet) -- As the number of smartphones users worldwide is expected to surpass 2 billion by the end of 2015, there's a growing opportunity for game developers to directly market games to messaging app users. Popular apps such as Line, WeChat, Tango, Facebook's (FB) Messenger, KakaoTalk, WhatsApp, Viber and SnapChat are growing their audiences globally, and $20 billion in revenue is up for grabs in the next couple of years.

According to Terence Fung, chief strategy officer at game developer Storm8, the global market for messaging apps has seen incredible growth over the last several years, with analytics firm Flurry recently noting mobile messaging app usage grew more than 100% in 2014. Fung added that in the U.S. in particular, recent comScore data show that 40% of mobile subscribers use an instant messaging app on their phone at least once a month.

Global mobile video game revenue will surpass $30 billion in 2015, according to research firm Newzoo. That will mark the first time mobile games will surpass console games revenue, which is forecast to top $25 billion in 2015, according to Newzoo.

Some of the leading messenger apps have been driving revenue for their parent companies. A big part of Facebook's success during the past 10 quarters has been mobile growth. Facebook has 1.19 billion mobile monthly active users and 745 million mobile daily active users with both numbers increasing as more people use smartphones and tablets regularly.

Tencent, which owns WeChat and QQ, saw fourth-quarter earnings climb 51% to $973 million thanks to increased game sales and advertising across these messenger apps' more than 1 billion active users. Next year, analysts forecast Tencent's yearly sales will surpass $20 billion.

"The Western messengers are still behind their Asian peers in terms of driving discovery of games, but there's huge potential given the increasing scale and reach of the Western messaging apps," Fung said.

Fung said Storm8 partnered with Viber Media because the Viber messaging app has 460 million unique users worldwide, which introduces a huge audience to games like Restaurant Story 2.

Jim Yang, vice president of games publishing at messaging company TangoME, said that in countries such as China, Japan and Korea almost everyone uses a messaging app not only for gaming, but for communication with friends and family. Even businessmen use messaging apps to communicate.

"Europe and North America are behind the curve of what's going on in Asia, but it's only a matter of time before messaging apps become big in Europe and North America," Yang said, adding that 30% of Tango's 275 million users are from the U.S. The company adds 300,000 new users daily.

Matthew Diener, qualitative analyst at research firm EEDAR, explained that in markets where social messaging services have secured a strong market share, they are nearly integral to the success of free-to-play games. For example, seven of the 10 top-grossing Google (GOOGL) Android games in Korea today are on KakaoTalk because it's incredibly easy for users to send invitations, challenges and lives to each other. He said this is valuable in making games go viral and is one of the biggest strengths of messaging apps.

Just as free-to-play games were established as a new revenue opportunity by game publishers throughout Asia, ultimately coming to North America and Europe later, mobile messaging apps are opening new opportunities for game developers as well. As such, investors will want to keep an eye on this new way to connect mobile gamers with new titles in a very crowded gaming field.

"There's been a great amount of synergy between the move towards the games-as-a-service model and proliferation of social networks, and I don't think that's a coincidence," Diener said. "It's far, far easier now for consumers to reach out directly to developers and publishers, and savvy developers -- both big and small -- are using social media as a means of communicating with their fans."

Lewis Ward, video game analyst at IDC, said messaging apps could emerge as an important advertising medium, but it's going to happen at a slow pace in the U.S. in 2015 because a lot of advertising dollars already committed to other channels.

But the numbers don't lie.

According to eMarketer, four out of five smartphone owners have played a game on their device and nearly half (46%) play games daily. In addition, eMarketer found that mobile is eating increasingly into other activities. Roughly 65% of all time spent online is through a smart device, while 32% of total mobile time is spent gaming. According to Google, 82% of users notice mobile ads. And Microsoft (MSFT) discovered that in-game ads can increase purchase intent by 24%, brand recommendation by 23% and overall brand rating by 32%.

"I think app providers, including Facebook and SnapChat, will go slow because they want to do tests to figure out what is a reasonable level of ads vs. an obtrusive amount for the user," Ward said.

Diener explained that social messaging apps really take off when they play to their strengths. Line and Kakao, for example, have attracted hundreds of millions of users in Asia because they're able to offer users an easy-to-use chat service that allows them to communicate in a visually pleasing manner.

"Investors should look for a good monetization strategy for casual users, but also have an eye for the gaming potential of a messaging service," Diener said. "Given the growth of messaging services from communication novelties to gaming platforms in their own right, he said it'd be fair to say that a messaging service needs to offer games if it hopes to compete with established players."

Tim Merel, managing director of Digi-Capital, said messaging apps can be fantastic for game developers if they have great games and can build a strong relationship with the messaging app owner. There are clear benefits around user acquisition and engagement, with the tradeoff being the margin paid to both messaging app owner and app store.

"Developers can work with messaging apps to reach high user volumes, but must pay revenue share to both messaging apps and app stores," Merel said. "For mobile games companies which haven't already achieved high user volumes, messaging apps might provide a good tradeoff to get a great game into the top 100 in a way that would not be possible standalone."

This article is commentary by an independent contributor. At the time of publication, the author held no positions in the stocks mentioned.