Hey David;
This topic has been hashed and re-hashed on this forum and the answer is always the same.....there is no answer, because the topic is too subjective. Everyone has there favorites and even reviews by the so called unbiased media still leaves a great deal of wiggle room when it comes to who or what is #1, especially when you're talking free options.
I use Link Removed due to 404 Error on Windows 7 Ultimate (64bit) and so far have been quite happy but as most people will tell you if they are being honest, you are the best antivirus that you could possibly own. A good, skilled and cautious user is always the front line of defense when it comes to malware and anti-virus protection.
As for the paid for commercial versions
#1 Eset Nod32
#2 Kaspersky
Just my opinion and there are sure to be others.