Last November Grand Theft Auto V topped 4 million physical retail copies in sales in the UK to become the best selling game ever in this country (beating Call of Duty: Black Ops). Chart-Track are now reporting (via MCV) that physcial sales in the UK have topped 5 million. Chart-Track doesn't track digital sales on PSN, Xbox Live or Steam, so it stands to figure that the number is significantly higher if those were also tallied.
The question is whether any physical release will ever reach the same heights as digital sales are becoming more and more prevalent.