If you liked the classic Ogame before all the p2w stuff was added, you'll like this game.
OGame - OGame is an addictive, Massively Multiplayer Online, Real-time Strategy, Space-war, and Money Management Browser-based video game develop by Gameforge AG.
Galaxy on Fire - Galaxy on Fire is a space combat and trading simulation.
Xterium (War of Alliance) - Xterium (War of Alliance) is a strategic space simulator in real time. Fight with thousands of players around the world at the same time to become the best. To do this you will need a regular browser. Learn how to manage a Space Empire!
SpaceHunt Game - SpaceHunt is a chat-based multiplayer adventure similar to Ogame and StarCraft: build a base and go on missions to explore the universe and attack other planets to gather resources and dominate the Universe.
Stellaron - Despite of the source that most OGame servers runs, we have revolutionized with unique add-ons that makes us distant from the typical OGame. Our contents are inspired on some 4x games such Civilization VI, Stellaris, Endless Space and others.
EVE Online - Player-created empires, player-driven markets, and endless ways to embark on your personal sci-fi adventure.