The one thing that the electoral college does is to insulate the system from State governments that effectively become single-Party dictatorships. Just imagine how a national popular vote would go if some State cast 50 million fraudulent votes for someone who ends up winning by 3 million popular votes.
I think this argument (though pretty unlikely to occur as stated) is probably the best one in favour of the EC. That is, disparities in state election laws means that the popular vote might not be a great reflection of the popular will. Then again, there's an easy solution (standardised federal voting laws) and even then it's unlikely any disparities caused by this are larger than what is normally caused by the EC.