Assassin's Creed 4 opening sales 60 percent down on Assassin's Creed III in the UK

Sales of Assassin's Creed IV: Black Flag are 60 percent down compared to last year's Assassin's Creed III in the UK, and sales of Battlefield 4 dropped 69 percent compared to 2011's Battlefield 3.

Many have said that the lower sales was due to the imminent release of the Xbox One and PlayStation 4, which both games are also being released for. Speaking to MCV, GfK Chart-Track director Dorian Bloch said the knowledge of how many people were waiting for next-gen was "unquantifiable."

"We’ve never had two must-have consoles launched so close together," said Bloch. "The unquantifiable question is, how many consumers are waiting on these franchises for a few more weeks?"

"How many PS4’s and Xbox One’s will have sold by Christmas? I would say, let the dust settle on 2013 and then we will know more."

The runaway success of Rockstar's Grand Theft Auto V on PS3 and Xbox 360 could have had a knock-on effect, too. "GTA V has completely blown everything away," added retailer Dixon's category manager Simon Urqhart.

"Gamers playing GTA are in no urgent need of triple-A titles right now. There will definitely be a surge in [Call of Duty] and BF4 players when the next-gen comes out and on Christmas Day."

FIFA 14, one of the UK's biggest games, also saw a 24 percent week-one drop over FIFA 13.

Assassin's Creed IV: Black Flag pipped Battlefield 4 to the top of the UK charts this week, with Call of Duty: Ghosts likely to take the crown next week.