While we won't have our review up until next week (embargos and whatnot), after several hours of playing, we can tell you what to expect when you're expecting Stellaris. They're similar in the same way Dota 2 and League of Legends are similar: anyone who hasn't played either game will think they're the same, but anyone who's played either know they're way different. In all seriousness, though, despite the genre and space setting, these are vastly different games. Actually, it might just be easier to explain how they aren't the same … hey, that gives me an idea!
Each game has Random Events, that can be queued by goings on in the galaxy or by investigating a planet you find, and you balance a complex economy of strategic and luxury resources that you can sell or trade to other empires.