Had the most fun with RTCW. That was the biggest fail of a demo release ever because like someone said there was no point in buying the rest of the game.
However MoH:AA will always remain the watershed moment of FPS games to me, even more so than MW, because this was the first time you were living a gritty movie in first person. It was exhilarating, exhausting, and overwhelming. Like RTCW though, the rest of the game was completely forgettable in comparison.