The first 3 movies were good only because the books were good; however Harry Potter 4 is a good movie on its own merits. While it would have been nice if a few loose plots were resolved, such as Rita Skeeter and Karkaroff, despite being based on a lengthier original the film feels more complete. Nor was, despite worries, Moody as disappointing as Lupin.

For some reason I had thought the Goblet of Fire was the Triwizard Cup, but that appears to have been incorrect.

Dumbledore is a house-elf.
Dumbledore is a Death Eater.