At an EU competitions hearing, Microsoft defended its proposed acquisition of Activision Blizzard, the maker of Call of Duty and Candy Crush.
Microsoft believes the $68.7 billion (£56.8 billion) deal will provide more options to gamers.
However, rival Sony, which also attended the hearing, claims that the merger would give Microsoft undue control over some of the world’s most popular games.
Sony owns the PlayStation, a major competitor to Microsoft’s Xbox console.
Microsoft president Brad Smith described the EU hearing on Tuesday as “an important day”.
He also dismissed Sony’s concerns that Activision Blizzard games, particularly Call of Duty, would be restricted to Xbox users if the merger went through.
“This was never about spending $69 billion to acquire titles like Call of Duty and make them less available,” he said following the hearing.
“That’s not a good way to turn a $69 billion asset into something that will grow in value over time.”
Activision Blizzard said in a statement, “We are confident that regulators will find that our proposed merger will enhance competition, create more opportunities for workers, and better games for our players.”
Nvidia and Google were also said to be present, despite the fact that the hearing was closed to the press and public.
Nvidia and Microsoft have announced a collaboration that will make Xbox PC games and Activision Blizzard titles available through Nvidia’s cloud-streaming platform GeForce Now.
The technology company must persuade regulators around the world that the deal, the largest in gaming history, will not harm its competitors. Microsoft had one last chance to present its case in Europe before the commission made its decision.