I've seen people who argue that Sins of a Solar Empire is not a "real 4X" but is really a conventional RTS.
I suspect most people are of the same mind as I on this topic: Sins of a Solar Empire is a game that combines 4X depth with real-time gameplay. That is what the game promises and I think that is what it delivers.
Here are some of the game mechanics of Sins that I think make it quite unique for a game that operates in real-time:
#1 Each race has about 100 different technologies to research. I just counted them up and if you count the military and civilian technologies plus the fleet supply technologies you end up with about 100. And that does not count the fact that many technologies have multiple levels to them.
#2 Players can win through multiple paths. I won a game on-line with culture on Saturday for instance.
#3 The pacing of the game is unlike any other RTS I've ever played. It's not about reflexes. It's not about how fast you click things. It's not about mastering hot keys to access special powers. It's about your ability to build a coherent, effective strategy to obtain specific objectives. OODA. Observe. Orient. Decide. Act. That is the essence of STRATEGY.
I could list many other elements but these 3 elements I think make Sins stand out from other real time strategy games. That is why people have compared it to a Kohan in space or Master of Orion in real time.
Certainly the game does not have the depth of say Space Empires V. But then again, neither does Galactic Civilizations. But the fact the game does not require manipulating a spread sheet or what have you does not make the game a non-4X game. Explore. Expand. Exploit. Exterminate. Sins of a Solar Emprie most certainly satisfies that.
The reason the game has become so popular with players is because there are a ton of people, people like me and I suspect like most of you reading this, that have waited a logn time for a game that is about STRATEGY. That lets us observe the strategic situation of a given map, figure out a strategy and execute on it.