There are a bunch of liberal perspectives arguing that scalia should be replaced with a liberal. But this will dramatically unbalance the court. Set your political views aside for a moment and recognize that the best situation that can exist is when the court is truly balanced--the nation has people of different perspectives. Not everybody agrees with you, and having a highest court that represents this diversity is the most open minded approach.
I frankly would hope that Obama's integrity would be such that he would nominate somebody with conservative values, just like Scalia, to replace the conservative seat he represented.