As far as Windows Anti-Virus products go, I've found for what they are supposed to detect... VIRUSES, they do all a fairly reasonable job... The problem is mainly that most 'threats' aren't traditional viruses, so an Anti-VIRUS can only guess, hence 'false positives'. The engine is detecting that the file may have a potentially malicious intent because of the level of access it might need to run it's operation or that the code is designed to violate copyright or rights management to allow the use of a non-purchased program.
Saga, I agree 100% with you, everyone has their own opinion, as an AV software is only as good as its engine and definitions, the one's that are updated the most frequent would be your best bet. I have been happily using AVG as a main anti-virus for the last 15 years. The free version has always found what real viruses I had on the system and alerted me if a potentially harmful app was downloaded or somewhere on the network.
AVAST - also very good - not a fan of the amount of resources that it and AVG use on 7 and lower systems (usually legacy systems without much RAM)
MSE - awesome - lightweight... if you're running an XP machine and have the 3.2GB RAM limit, I suggest this to allow you the most possible resources for the system activities.
Avira is decent... used it's full package until some license issues showed up
BitDefender - if you don't like CLAM AV this works on Server
CLAM AV - another AV - in lots of bootdisk scanner packages (ie TRK; Hirens; UBCD)
Those are the main Free ones - most have the option to pay which will generally give you faster access to updates and different scanning options, some will add a firewall software
Then the standard consumer boxed copies (I never suggest but am not going to remove if you have an active subscription)
Norton (any security product) - decent definition support - hog on resources no matter what Symantec wants to say
McAfee - pretty good update releases, can't say it's too efficient on its resource management
Kasperskey - one of the Virus labs I trust the most... they infected / disinfected a Ford (think it was an Escape) before anyone thought that was a potential infection path (Bluetooth)
ESET (NOD) - usually only use their online tool but previous use of the consumer program was still decent
Really I would suggest one that you are familiar with and can understand the UI. If you've been using AVG for the last while stick with that, if you've been using Norton and prefer not to learn something new use that.
I would highly recommend though getting a stand-alone malware removal program on there. The previously mentioned Malwarebytes Free is great, however an after-the-fact type of tool. If you register it (~$30 USD) you get a lifetime subscription priority updates and on-access malware scanning. I'd say worth it, but you be the judge.
Spybot is decent, but the UI isn't as intuitive as Malwarebytes (MBAM)
It wouldn't hurt to make a Windows Defender Offline (WDO) scanner disc also so if you get a nasty infection that prevents explorer from loading properly (RCMP/FBI UKash infection and the like) you can then have a bootable malware/virus scanner that after some updates (on hardwired) can generally open the machine up again to give you access to MBAM or you AV software to remove.
Online scanners I would suggest also include:
Panda Cloud
Panda ActiveScan
Eset Online
Hitman Pro
Hope this helps.... Overall No one scanner is king, but using all available tools properly will get rid of most infections that are around these days without removal of user data.