Northern Lights are best to be seen on the earth's North Magnetic Pole (not North Geographic Pole), it is anywhere in the northern hemisphere that circles round the northern magnetic circle.
Northern Finland (Lapland), Northern Norway (Tromso), Iceland, as well as Northern Sweden, Alaska & Canada are all essentially the best locations to see the Northern Lights. There is no strict answer as to which country is the best choice. The best viewing location varies from year to year according to the northern magnetic circle movement. Clarity & brightness of the Northern Lights are dependant very much on the time of year, solar activity, and various environmental factors.
Windboat, if you really want to see Northern Lights in Europe, head to Lapland, Tromso and Iceland for they all fall in the zone of greatest probability!