Ok this post is 3 years old but just waiting to be answered - yes you can get decent imported beer here! Your 3 best options are:-
1. The big supermarkets - RT Mart, Tesco, Auchan, Wal Mart etc all carry imported beers - Tesco (in the basement of Lippo Plaza on Hanjiang Lu just north of the West Bus Station) has the best choice including Duvel, Leffe, Erdinger, Newcastle Brown Ale, Strongbow Cider etc.
2. Metro -the big German cash and carry warehouse on Jiangyang Lu 1 block west of the West Bus Station - you need a members card to buy here so if it's your first visit bring your passport and business card in order to register as a member. They have a huuuuuuuuuge choice of imported beer but you can only buy mulitpacks, not individual bottles, however most work out at 15-20RMB per bottle as opposed to 25-30RMB a bottle in Tesco et al. They are also good for decent western style bread, cheese, meats etc.
3. The Ivy Food Store on Huaihai Lu (just north of the intersection with Siwangting Lu on the right side) usually has a small selection of German beers as well as a nice selection of imported foods (biscuits, chocolate, breakfast cereal, condiments etc) and prices are quite reasonable compared to imported food stores in Nanjing, Shanghai, Suzhou etc.