Stellaris, or the space RTS that lets you encounter exciting new alien species, enslave them, and eat them, reached its three year anniversary. Developed by Paradox Interactive, the game is a mixing pot of features that would’ve likely been impossible to implement decades ago. Typically RTS games focus on combat and relegate things like diplomacy to being a secondary feature. With Stellaris, you have to manage your empire’s economy, foreign relations, research, military development, and military actions on both a galactic and planetary level. And that’s just the surface of what makes Stellaris such a potentially addicting game.
As cliched as it may be, virtually every choice that you make in Stellaris can have consequences later on. In fact, one of your very first choices, your empire's form of government, affects how other empires treat you. Play too aggressively, and other empires can band together to form a defensive alliance. Opt for diplomacy, and they may treat you as an ally. This can prove useful when one of the endgame apocalypse scenarios trigger. After all, you wouldn't want to face an invasion on a galactic scale by yourself. It would make for a good story though.
Being an RTS, some parts of Stellaris have an immense learning curve and will thus be off putting to newcomers. Fortunately, the basics are simple enough. You have to manage three primary resources to keep your empire running and your military ready for action. Once you get beyond the basics, things can get overwhelming. Important members of your government, such as your scientists, will die. Your citizens can get unhappy with your method of ruling and rebel. The very planets that you colonize can have glorious treasures or hidden monstrosities. This is the double edged sword that gives Stellaris such unprecedented depth and frustration.
While Stellaris' core gameplay is quite good, it wasn't always this way. The game was never terrible, but there are some drastic differences between how certain features work now and how they functioned three years ago. Perhaps a more accurate statement was that the gameplay was not as polished. Combat in particular underwent quite a number of tweaks, balancing and otherwise, so that it's not a complete chore to invade or defend a planet. Multiple updates tweaked how planets and populations interact with each other. Government, culture, and exploration have been drastically expanded to the point that an entirely new upgrade/research tree was added to the game. This is all before you factor in the DLCs. Enable all of the DLCs, and you can build weapons that can destroy planets, create megastructures to harness the power of stars, and even witness a galaxy spanning fight between extremely powerful precursor alien races.
All that being said, it can be argued that the greatest strength of Stellaris isn't in its gameplay. Instead, Paradox Interactive, the developers of the game, deserve an immense amount of praise for their post launch support. To this day, they are working on new content. While you have to pay to get access to the flashier parts of Paradox's DLC, all of their DLC have free, mostly significant, features. It also goes without saying that Paradox is relatively quick on releasing balancing and general maintenance updates.
Unfortunately, there are two rather large factors that hold Stellaris back from being a "perfect" game. The first is that the game is in no way casual friendly. Actually, it might be safe to say that it's not very friendly at all to anyone. If you want to dive in as a new player, you're going to get overwhelmed by all the menus and information that's being thrown at you. If you want to return to the game after missing a couple of updates, chances are that Paradox added some new features that will seem ridiculously complex. The second negative factor is that the game is rather slow. You're not going to be able to finish a match in 30 minutes or less. If anything, a standard match might take 30 hours to complete. The massive time commitment that Stellaris demands is not exactly Paradox's fault, but they definitely made things "worse" with each update. On the bright side, there is no shortage of mods that you can install.
In some ways, Paradox are victims of their own genius with Stellaris. It's an amazingly in-depth game, but there is no chance that it's going to appeal to the masses. On the other hand, Paradox did effectively corner a niche market with Stellaris, so if you really like space RTS games with absurd learning curves, then there are few alternatives. Regardless, it's rare that a three year old game not only retains the quality that it had at launch, but surpassed it. It's rarer still that a developer is seemingly so enthusiastically committed to a game.