MSE is one of the higher rated AV Apps out there now. It has been ranked right up there with the other top dogs. The problem is that any AV runs on definitions, so any new Aero-Day infection that comes out is not protected against. Since there is no definition to block that infection at the time of release, there is no AV app out there that can protect you against such infections.
An AV app is only as good as the person using it. If you go to shady corners of the internet, you cant rely on your AV app to protect you. The reason is that you never know what is on these sites. It is quite easily that these sites contain an infection that can get around one or all security apps out there and cause destruction like the one you got did. So your best defense is to use a combination. Use something like Avast, MSE or AVG in conjunction with something like MBAM to try and stave off most infections. If you are going to go to more untrusted sites on the internet, use a more secure browser.
Something like Firefox with the FlashBlock, Ad Block and NoScript extensions. Chrome with its similar extensions or even Opera that has a combination of similar extensions. That way you block just about everything the site can throw at you and stay protected. Using Sites like Facebook, never click any link. Install something like WOT (Web of Trust) or McAfee Site Advisor or the AVG Site Advisor to stay protected. They will tell you how other users rate such sites.
The most important lesson is to backup regularly. That is a lesson that is hard learned.