The newer games are a little too new wave for my tastes, but when Battlefront 2 came out in '04, I think Pandemic really came into their own, commercially and artistically. The whole game has clear, crisp gameplay, and a new sheen of consummate professionalism that really gives the game a big boost. It's been compared to Battlefield, but I think Battlefront has a far more bitter, cynical sense of humor.
In '05, Pandemic released this, Battlefront 2, their most accomplished game. I think their undisputed masterpiece is "Tatooine: Mos Eisley", a map so fun, most people probably don't pay attention to the game. But they should, because it's not just about the pleasures of gaming, and the importance of trends, it's also a personal statement about the company itself.