I have a 2003 BMW 325i (16" wheels) and I started with the OEM (ContiTouring Contact) and went to Pirelli PZero Nero and then onto Michelin Pilot Exalto A / S.
The Pirelli's were a step up from the OEMs (quieter, better in wet, and snow) but the Michelin's are significantly better than the Pirelli's. They are significantly quieter than the Pirelli's and give a great ride with good adhesion in wet and snow (I live in Chicago so we get some snow and ice.) While they're expensive, they're amazingly good.
I've had great luck with Tire Rack for my last three sets of tires.