Microsoft outsold rival by more than 4:1 in 2012, according to Chart-Track data
Lifetime Xbox 360 sales look certain to overtake those of current-gen leader Nintendo Wii in the UK.
Nintendo UK confirmed before Christmas that around 8 million Wii consoles had been sold in the UK.
Despite a reported 33% decline in video game console sales last year, Lifetime Xbox 360 is said to have outsold its current-gen rivals by a "significant margin" in Britain during 2012.
Nintendo DS and PlayStation 2 remain the UK's first and second best selling games consoles respectively, with Wii and Xbox 360 currently in third and fourth spots.
Globally Nintendo still has breathing space between itself and its current-gen rivals.
As of September 2012, Wii had sold through 97 million units, compared to Microsoft's 70 million Xbox 360s sold worldwide (October 2012) and Sony's 70 million "sold in" PS3s (November 2012).
In the US, industry research firm DFC Intelligence predicts Xbox 360 will also overtake Wii to become the region's best selling system for its generation.
Unlike Nintendo, Microsoft has seen its console peak during the later years of its life-cycle, the firm wrote in an analyst note this month.
"The success of Microsoft and the Xbox 360 during the past two years highlights a radical changing of the guard in the game industry.
"Much has been made about a steady video game sales decline in the past three years. In reality the decline has mainly been due to the aging console systems and more importantly because of Nintendo's collapse."
Nintendo president Satoru Iwata suggested earlier this month that Wii U sales "are not bad, and I feel it's been selling steadily", although he admitted to unbalanced inventory levels after the company failed to anticipate the amount of demand for the premium version of the console.