Its not really 25 fps. Basically on tv you have two pictures at 25 Hz which together combine into a complete picture which is at 50Hz. 60Hz for US/Japan...
Off-topic:
Movies also use motion blur techniques in between frames to make things smooth. Many newer games do the same thing, Crysis for example. It's very playable at 25 fps. Quake 3 Arena and older games don't use motion blur that's why you need high number of frames.
