sanjay manjrekar is one of the most biased commentator i've heard lately. you should've heard him in the latest pak-ind series.
ravi shashtri is one of the best though. Always enthusiastic and not taking any sides, no matter who's playing.
I also like ranjit fernando (Sri Lanka) and Asif iqbal, the pakistani player who used to commentate a lot in sharjah, not anymore though.