Okay I will go into this.
I have used alot Anti-Virus some is crap some is good. I have also witness good anti-virus (via Trojans hence the reason why 70% of the people I talk to ask trojan advice since I am a master)
Okay the best I have found hands down is
AVP or Kaspersky Anti-Virus
Reason why I got it the first time: All the makers of trojans use this, all the super elite trojaners use this, and it is clearly the best.
A next one I have heard from many trojan people have started to recommend now is Macaffe. They are starting to get off there lazy asses and do better.
Those are from the trojan world. Now I check to see what was hot in the file sharing world (kazaa, edonkey, overnet networks) and this is what they like
Panda Anti-virus (It looks like a AVP clone)
AVG (AVG is free)
Fsecure (I am currently trying this one)
I would not recommend Norton.
Why: It does not cut it. Norton makes alot of mistakes (like the JS.Exception on mewgoods site) and does not scan well. Infact I put it on my mothers computer to give her a sense of false secruity.
What I recommend:
AVP and Fsecure