The UK tells a slightly different MGS4 sales tale. MGS4 is the second fastest-selling PS3 title behind Grand Theft Auto IV and was 14,000 short of MGS2's initial sales in 2002. Although the UK's Chart-Track apparently did not release actual numbers, the company's director did say that MGS4 had a "minimal impact" on hardware sales and that "there's not a lot to say about it."
Unless Sony or Konami sends out a release, we're not expecting US sales figures until NPD's June report releases sometime next month.
Source: Famitsu (translation) report (Via IGN)
Source: Chart-Track: MGS4 had "minimal" impact on UK PS3 sales