Hi,
As we can see from the above comments, there is no "best" Antivirus. However, I can recommend you a few products which based on my experience I would pick other other products. Each product has different strenghts.
Paid: ESET (recommended due to the good detection rate), Emsisoft (recommended due to the Behaviour Blocker) or Kaspersky (recommended due to the Application Contol feature).
Free: Avast
Antivirus, Avira Free
Antivirus.
Please note the above is
just my opinion. It is up to the user to decide which product should be used on their system/s.
If you'd like to learn more about why there is no "best" Antivirus, please read the information available at the following thread:
http://malwaretips.com/threads/why-there-is-no-best-antivirus-product.44676/
I recommend you test out the products using the free trial they usually provide and then after testing a few decide which one you prefer out of the ones tested.
With this in mind, please remember that no Antivirus/Internet Security is there to protect you 100%. It's also down to the user just as much to be careful.
Cheers.