The most popular platforms for building an online shop in Greece include Woocommerce + WordPress, Magento, Prestashop, Opencart, and Shopify. Woocommerce is an open-source platform known for its flexibility and customization capabilities. It offers a wide range of plugins and themes to help you create the perfect store. Magento is another popular choice, offering a broad range of features and tools to build a powerful online store. It also provides a high level of security and scalability. Prestashop is another favored option, offering features designed specifically for e-commerce. It also provides a variety of themes and add-ons to customize your store. Opencart is also popular, offering user-friendly management and features. Finally, Shopify is a well-known platform for its ease of use and wide range of features. It also offers a variety of themes and plugins to customize your store.