The site topic is clearly labeled as the first week of sales in the US, I'd be surprised if he misunderstood that. Although it's possible he's looking at it from how many we're sold to retailers, I know my local Best buy has like 20 copies sitting there, so it's possible a much large number was shipped out to stores.

I would be careful about assuming that Mass Effect is being significantly undertracked. If anything, the recent trend for VGChartz software has been overestimating high-profile titles, not underestimating them. Bioshock, Metroid Prime, Heavenly Sword, Ratchet and Clank, the Orange Box, and Guitar Hero were all games that saw numbers sharply reduced downwards after later data came out. I have no idea if that's the case this time again, just want to issue fair warning.

Mass Effect looks like a fabulous game, and I hope it sells well. Just bear in mind that the track record of 360 RPGs has not been very good outside of Oblivion (think of Blue Dragon, Eternal Sonata, etc.) Remember the "Zak and Wiki" effect: just because a game is loved by the Internet hardcore community does not mean it well necessarily sell well to the general public.

Here's hoping I'm wrong though.