which is the best antivirus?
Asking this question is like asking which do you prefer Nvidia or ATI? AMD or Intel? XBOx 360 or Wii or Playstation? You'll get a ton of answers.
Do you want a $ version or a free one?
If it is payed I say NOD32 or Kaspesky. Both are excellent and tech support is superb. AVG, Anti-Vir and Avast are also very good.
Anti-Vir and Avast have very good free ones.
I would avoid McAfee and Symantic though to be fair the new Symantec 360 has a much better reputation than its's earlier versions. Norton was a system hog.
The search feature is your friend.