There's no "best" virus protection. It's impossible to recommend any AV software, because their so-called protection fails in so many ways against so many virus that it isn't funny.
Be sure to avoid paid-for products. The bunch of crooks that the AV software industry is, for selling highly defective products at high price tags and thereby making billions of dollars each year, needs to be hit at the wallet.
Over the years, I've fixed multiple computers that were ridden with virus despite the presence of an up-to-date AV software, whether paid-for or free. I usually ended up detecting the virus manually, by examining the various startup entries, finding files with strange names in select directories, etc.
And after finding the virus, I usually sent it to VirusTotal... the "best" result I got was one third (!!!) of their AV software roster (of 36 and later 42 programs) detecting the virus as such. Sometimes, only one or two AV software pinpointed the virus - and it was usually through heuristic detections (which only means that the virus was not obfuscated well enough...).
And the trend of virus technology is constant evolution towards higher sophistication. Have you read about the Stuxnet attack (whose sophistication shows that it's the work of up to several hundreds of man-months of work !), or rootkits with memory forging capability, just to mention two disturbing trends ?
Nowadays, malware isn't done by amateurs, but by money-motivated criminals (sometimes backed by their governments). And every day, facts show that the AV software industry scam is doing an extremely bad job at "protecting" against such threats....
One last note: keep in mind that security on the one side, and ease of use on the other side, are highly antagonist features. Consumer software is in the "easy to use" category, but therefore, it's in the "insecure" category. Strong hardening (e.g. the huge grsecurity patch to Linux) carries costs in usability and performance.
