But occasionally a review appears that fully justifies the feeling that there is a bias towards other brands, and the one below is a classic!
These lens tests were from the Photography Monthly magazine Macro Lens round-up, June 2007. Left hand chart and verdict Canon EF-S 60mm f/2.8, right hand Pentax SMC-D 50mm f/2.8 (click on the pic to open a larger version).

Just take a second to note the score for each lens under 'Performance', then have a look at the resolution charts. Hmmmm...
According to the reviewer "where it (the Canon) does score well is wide open at f/2.8", whereas "at the wide apertures below f/5.6, the (Pentax) lens is a little disappointing".
Hence the reason magazine reviews are held with an air of scepticism round here.