Wayne Bridge is probably the best left back we have and he's not exactly great. Then I'd say Warnock, a lot of pundits agree too just not the 'pundits' on MOTD. Not seen a lot of Bale yet but he looks like he can defend and most importantly get attacks started, so definitely one for the future. Shorey on the other hand, had a terrible game against Germany and in my opinion is easily replaceable.
Oh and Ashley Cole... definitely the best left back in the world if you're Motson but if you can see you know how average he really is.