Malwarebytes is certainly the best anti malware scanner by far at the moment (although they are being sneaky in trying to get you to use the paid for version by giving you a prompt you have to decline when you install the free version otherwise it starts a short trial of the paid for version)
There are plenty of perfectly good free anti-virus products that will give the average, home, user ample protection (AVG, Avast, MSE, Commodo are all good enough)..... but that said there is also nothing wrong with the well known paid for solutions and as most of them can be had for about £20 a year it's hardly a huge expense and some people seem happier with them (I think some people can't accept that you can get something that works for free)