I would say that the top ten most famous computer antivirus software programs are:
- Trend Micro
- Bit Defender
- ESET Nod32
This is not to say that they are the ten best, but from my experience working at a computer repair company, I would say that they are the ten most common.
In terms of making the choice yourself, you really need to consider what you are using your computer for.
If all you do online is check your emails, there is really no need to spend a great deal of money on a really comprehensive antivirus, and so one of the free versions such as AVG or Avast should be fine.
Whereas, if you use your PC for downloading, web browsing and torrenting, you might want to consider a paid version which offers greater protection.
Personally I have always used ESET Nod32 on my Windows machine (I don't bother on my Mac).
Although you have to pay for it, it is reasonably priced and runs along quite unobstructively in the background.