Hokkaido's big. Look at that big chunk of red up there. That's like seven prefectures in one. A lot of cool stuff fits in all that land. There's a reason Koichi loves it best.
Hokkaido is cold in the best way possible. The snow festival, snowball fighting championships, and hot, hot food make winter in Hokkaido a delight. The Ishiya Chocolate Factory and Sapporo Beer Museum are visits you can taste. Mt. Hakodate has a breathtaking view. The outdoorsy types will feel right at home in Hokkaido (and maybe never leave).
If you don't like winter, you need to visit Hokkaido. It's a prefecture for all seasons.