The record-breaking title still managed to outsell Nintendo's Wii Fit – which held onto second spot – by 4-to-1 in the week. The Nintendo title saw a sales drop of 48 per cent week-on-week.
Meanwhile, the Xbox 360 version of GTA widened its sales advantage over the PS3 version by accounting for 62 per cent of sales, compared to 55 per cent last week.
Elsewhere in the chart, Nintendo's Wii Play climbed one place to third, swapping positions with Sega's Mario & Sonic at the Olympic Games.
Sega also enjoyed a strong second week for Iron Man: The Official Video Game, which rose from eleventh spot to fifth.
Every remaining game in the All Formats Top 40 lost sales in a slow week – except 2K Games' Carnival: Funfair Games, which enjoyed a sales jump 25 per cent. The title climbed from No. 37 to No. 22.
The full top ten for week ending Saturday, May 10th reads:
1) GTA IV (Rockstar)
2) Wii Fit (Nintendo)
3) Wii Play (Nintendo)
4) Mario & Sonic At The Olympic Games (Sega)
5) Iron Man (Sega)
6) Call Of Duty 4: Modern Warfare (Activision)
7) Pro Evolution Soccer 2008 (Konami)
8) Gran Turismo 5: Prologue (Sony)
9) Mario Kart Wii (Nintendo)
10) Dr Kawashima's Brain Training (Nintendo)