David Pitkin, who works for Ubuntu developer Canonical, said he now expected "a growing number of game developers to include Ubuntu among their target platforms".
Currently, few game makers produce a version that can run on Linux or other open-source operating systems.
While almost 60 titles are available on Steam, the store sells more than 2,000 games that run on Windows.
The launch is important for Valve because Linux is expected to be the operating system for the console it is developing to allow Steam games to be played on TVs.
As the curtain was being lifted on the Linux store, Valve sacked about 30 members of staff including high-profile developer Jeri Ellsworth who was reportedly working on the hardware behind the company's console.
Valve boss Gabe Newell took the unusual step of issuing a statement about the lay-offs to curb speculation about what they would mean for the company's many projects.
He said the sackings did not mean it was cancelling any projects or changing its priorities.
"We're not going to discuss why anyone in particular is or isn't working here," he said.