Below is the list of recommended Magento 2 themes selected for quality of the code, speed and included features.
Ultimo is a premium Magento theme with advanced admin module. It’s extremely customizable, easy to use and fully responsive. Suitable for every type of store, optimized for SEO. Includes multiple variations.
Shopper – is an extremely powerful and flexible premium Magento theme with responsive & retina ready design. This elegant theme is a great fit for a fashion and accessories store.
Manhattan – is a premium Magento 2 theme which will work well for electronic store, a mall or any store with a large number of top level categories.
TV Suunhi – is a responsive Magento 2 theme great for a clothing / fashion store. Has 6 variations to choose from. Done on Bootstrap.