This app was mentioned in 2 comments, with an average of 1.00 upvote
Yeah, good games are very rare on mobile platforms. I had some fun with Star Colonies. It's something like 3/4 Galcon and 1/4 full on 4X. Like Galcon, it's real time, with only one unit type that does both space combat and colonization but you can build buildings, manage resources, and you can research upgrades. Shame that the game has only so few maps, no random maps, and no more updates. Full version is not even available on the Play Store anymore. Here is link to the demo version, APK of full version can probably be found on some "backup" site:
https://play.google.com/store/apps/details?id=com.blueplop.starcolonies
Uciana is a proper 4X on Android, visibly inspired by Master of Orion 2. I recommend it, it's worth more than it's price tag:
https://play.google.com/store/apps/details?id=com.birdshel.Uciana
The absolute best game to have on a mobile, in my opinion, is Uniwar. It's not a 4X, instead it's a turn based tactics game, with Starcraft vibes. It's the one I've installed on every smart phone I had so far. And I even play it online since it allows for very relaxed schedule:
https://play.google.com/store/apps/details?id=android.uniwar
There is a similar game, Strategium but I wasn't able to get into it since it was exclusively in cyrillics when I tried it. There are a few odd but good games from Yoitro:
https://play.google.com/store/apps/developer?id=Yiotro
I personally like Achikaps and Antiyoy from him.