NOD32
then Kaspersky
then Trend Micro (not recommended)
then McAfee (recommended even less)
then Norton (don't touch with a 2000 foot pole)
Trend Micro used to be very good, but they became complacent. It detects slightly more than McAfee, but still misses a lot. McAfee is a resource hog. Sometimes I feel even if I had 20 GB of memory, I would still need more with McAfee. And Norton is the biggest piece of junk out there. It detects viruses but misses most spyware. I wouldn't trust Norton for anything. The one advantage Trend Micro has is great parental controls, which also include protection for 99% of the malware infested websites.
NOD32 is the best. It is lightweight and it detects any and everything. The only minus is it isn't cheap.