Camden Yards has excellent service and the concession lines move quickly. STL same thing. Those two parks stand out from my visits. Quick efficient yet personable service. Id settle for quick and efficient for now.
Although the Beers Around the World vendor near section 111 have the same guy and woman for several years - they hustle to serve the customers and do an admirable job- the Cell probably needs a third stand on the lower level as there is always a line even on slow game days.
"Call your sons! Call your daughters! Call your friends! Call your neighbors! Mark Buehrle has a perfect game going into the ninth!"