Well...
George II married Caroline of Ansbach, who was German.
George III married yet another German princess, Charlotte of Mecklenburg-Strelitz
George IV married Caroline of Brunswick - you guessed it, a German princess (and his cousin)
William IV married Adelaide of Saxe-Meiningen - guess what she was?
Queen Victoria was descended from George III. Her father, Prince Edward, married Victoria of Saxe-Coburg-Saalfeld. Which would make her a German princess.
Her son though, broke with tradition and married a Danish princess, as Nemowork mentioned.
Mr. E. Blackadder's opinion of Caroline of Brunswick can be seen here, at 05:19 in the video: