It's always fun to read amateur AV tests... except when it's simply depressing.
One major factor the testers usually manage overlook is that, though tens of thousands viruses have been written since the seventies, 'only' about 2700 viruses actually circulate at the moment. Those are the viruses that need to be detected, not the DOS virus written in 1983 that only exists in AV company databases.
See
http://www.wildlist.org/ for a list of currently circulating viruses.
See
http://www.virusbtn.com/ for regular tests of AV products using the wildlist.
For those who don't want to sign up: Avast has 100% scores up to and including the Nov 2004 test. Earlier on, Avast's performance was far worse, but that has no impact on current results (as long as the hard-working people at Alwil software don't start to goof off).
The other two gratis scanners, Grisoft AV (AVG) and H+BEDV (AntiVir), have a similar track records, shaping up in mid-2004 with 100% scores.
Of the two most famous scanners, Norton did fine while McAfee missed in Feb 2005.
Kaspersky and NOD32 stand out as notably reliable scanners.