For me it has to be Mourinho on RT.
Very good analysis, tells you something you probably didnt notice or knew (tactically) and you can tell he knows the game inside out and is very concise with his answers/views. He looks stress free and is also appearing quite charismatic.
Cesc Fabregas has been quite impressive on the Beeb, showing some good sense of humour.
Henrik Larson and Slavan Bilic have also been really good on ITV. Drogba has been very poor in my view, monotone voice.