Microsoft has said it expects the numbers subscribing to Xbox Live to rocket thanks to the success of GTA IV.
Released on 29 April, sales of the game broke first-day record sales on both the Xbox 360 and PS3.
However, early numbers suggest that the Xbox version is fast outselling Sony's offering, many attributing the extra downloadable content available for 360 gamers as the reason.
Talking of its success, Aaron Greenberg, director of product management for Xbox, said: "It will likely be the the best-selling game launched all year and we expect it will drive a lot of new members to Xbox Live".
He added: "The multiplayer in this game is so well implemented that I can't imagine anyone owning a copy without trying to play it on Xbox Live".
Billy Pidgeon, IDC analyst, agrees by saying that the game could eclipse the current Xbox Live favourite of Halo 3 and attract consumers who aren't interested in first-person shooters – the dominant online genre.
"I think the console, even more so than the PC, has the potential to have lots of different types of games be popular online."
"GTA is an important piece of that. It can lead the way online for a large contingent of players who don't play first-person shooters."