I thought this was a good article from PC Mag, and tend to agree with their comments.

http://www.pcmag.com/article2/0,1895,2304349,00.asp

My personal preferences are Sygate, Avast, Threatfire, and SuperAntiSpyware Pro, and I like the Windows Live OneCare scan for a second opinion. Everyone has their own opinion on what is best but these seem to work for me and I think that Realtime protection is more important than cleaning up afterwards.

Cheers