You can look up reviews of software such as this
one. The trouble is though that all these different reviews use somewhat different methods to evaluate the various software packages, and as such their rankings will be different.
If you want some suggestions from Bleeping Computer
members then please let us know what you are after.
Free or paid for version?
Anti-virus only or a suite containing anti-virus, anti-spyware and firewall?
I am currently using AVG Anti-virus (free) and am happy with it.