I've already mentioned this twice in other threads, but I may as well mention it again because it's really good. Stellaris! It's a cross between the 4X space strategy genre, and the signature Paradox Grand Strategy games (Hearts of Iron, Crusader Kings, Europa Universalis, etc.).
The diplomacy and economy is a lot more straightforward and Civilisation-like than most PGS games though, and I've heard that turned off some of the core fans, but honestly it's only because of the slight dumbing-down that I was able to get into it. Other PGS games have always been a pain for me, fun at times but mostly just frustrating micromanagement and a lot of memorising. Stellaris is my current favourite, though more options when it comes to managing your empire wouldn't hurt, but hey there's mod support for that.
That tends to be my pattern with strategy series really - try one, didn't like it, wait some time, it gets dumbed down, play that one. Nice to see the "dumb-down" thing actually work in my favour for once, and it's a new IP and not an existing one so core fans shouldn't mind. Still looking forward to Hearts of Iron 4 though, maybe this time I might actually get into it now that I've had a hand at one of their other games.