Depends on what you're looking for... generally there is a tradeoff between detection rates and system impact. If you have a fairly fast computer >2 ghz , nothing tops Kaspersky. McAfee is a close second but has some bloat, though not as much as Symantec.
(click on comparatives) is a good site to check things out. It has two kinds on tests... a straight detection test using the most up to date signatures and a retrospective test. The retro uses old signatures and tests the AV apps ability to detect threat patterns with baddies that came out after the signatures.
Rokop is a german site, babelfish takes care of that, but the guys are very knowledgeable. They have some rollup results... www.rokop.de
have to do some searching.
Don't believe one thing you read when it comes to mainstream publications like CNet, PCMag etc.. marketing dollars buys the results and keeps the competition low (as in not a full spread of AV apps tested)... and the testers are generally incompetent.
FYI Trend Micro blows, horrible detection rates. You'd be better off with Symantec which isn't a huge step up.
I personally use NOD32. Very light, great detection rates. I use Kaspersky as my backup scanner.