The whole seven sisters is a work of nature, and must visit for every individual. Personally, I have been to Sikkim, and it was breathtaking. Also, Meghalaya is very famous for its hidden waterfalls, and bridges.
North East is very big. Prepare your wish list . one has to have sufficient time to explore properly. Decide your starting point first. There are places which are well connected .Better take a road journey to take the wines of this area of our country