Grand Theft Auto 4 and Episodes from Liberty City are now backwards compatible on Xbox One.
Rockstar's greatest hits are heavily discounted this weekend on the Humble Store.
Exclusive games and downloadable content are "critical" for the Xbox 360, Microsoft has said.
Exclusive content - even if it's only for a set period of time - is crucial for differentiating the Xbox 360 from the PlayStation 3 and Wii, Microsoft's European boss Chris Lewis told Eurogamer.
"They are important," he said. "DLC windows of exclusivity are critical for us for differentiation. We'll continue to bring those exclusives through our own studio work, Gears and Forza and other titles."
Rockstar has decided to bundle up the Grand Theft Auto IV family into a special edition compilation due out in the States at the end of this month.
Stab-'em-up series Assassin's Creed will be as big as Grand Theft Auto "in the not-too-distant future", Ubisoft reckons.
Just a few weeks after the game's release, Take-Two has announced that more than 5 million copies of Rockstar's Red Dead Redemption have now been shipped.
Rockstar has told Eurogamer it cannot comment on how long the Grand Theft Auto IV downloadable content was exclusive to Xbox 360, although in hindsight it appears to have been a 12-month deal.
Just under 14 months elapsed between The Lost and Damned appearing on Xbox Live and its eventual appearance on PS3 this month, suggesting the deal may have been measured from the release of the first add-on (the second, The Ballad of Gay Tony, arrived relatively recently on Xbox 360 and is already available for PS3).
Microsoft also wouldn't verify the length of the exclusivity deal to Eurogamer. The platform holder reportedly paid millions and millions of dollars to secure it in 2006. Sony pointed us back to Rockstar and Microsoft.
Sony has updated the PlayStation shops with all manner of treats - and the promises of the GTA IV downloadable episodes, which are both due to go live tomorrow.
Rockstar has announced that The Lost and Damned and The Ballad of Gay Tony have been delayed on PC and PS3 due after Sony asked for some changes.
Games industry analyst Mike Hickey has said a Grand Theft Auto V announcement may be on the way - and that it could be made before E3 kicks off in June.
"There is building suspension for a pre-E3 GTA V announcement," he said, as reported by Industrygamers. "Although we expect nothing from Rockstar at this year’s official E3 event."
Rockstar is more likely to hold a separate press event and make the announcement independent of any publisher conferences, apparently. That's because GTA V really is kind of a big deal.
Former Tory leader Iain Duncan Smith has claimed videogames are messing up the kids with their crazy violent ways.
Rockstar may well be teasing the next Grand Theft Auto game or DLC in the packaging for Episodes From Liberty City.
The BBFC has revealed there are some "strong" sexy moments in upcoming Grand Theft Auto IV downloadable add-on The Ballad of Gay Tony.
Rockstar has confirmed a UK price for the disc featuring both episodes of the Grand Theft Auto IV DLC.
Rockstar has announced the next batch of downloadable content for Grand Theft Auto IV will be available via Xbox Live on 29th October.
The Ballad of Gay Tony will see you playing as Luis Lopez, who works for nightclub boss Tony "Gay Tony" Prince. As previously announced it will cost 1600 Microsoft Points (GBP 13.60 / EUR 19.20).
Or you could pick up Grand Theft Auto: Episodes from Liberty City, a disc release featuring both DLC episodes released so far. It's also out on the 29th and will cost $39.99 over in the States. We're checking with Rockstar for a European price.
Rockstar has announced that the second Xbox 360-exclusive downloadable episode for Grand Theft Auto IV is called The Ballad of Gay Tony and is due out this autumn.