Microsoft SharePoint is the enterprise portal and page-building platform of Microsoft 365, with 400 million+ commercial users, 100+ Web Parts and 3 site types for building intranets and publishing content pages.
Google Sites is a free lightweight site builder released by Google in 2008 and redesigned in 2016, free for personal use with deep Google Workspace integration, ideal for project pages, intranets and simple landing pages.
DNN (DotNetNuke) is an open-source .NET CMS that originated in 2002, deeply integrated with the Microsoft stack, with built-in native multilingual support and granular permissions, plus 1000+ extensions in its marketplace, ideal for enterprise portals and intranets.