The prequel I sum up as one deep and satisfying game of chess with aliens and plasma rifles. XCOM 2 is so much more.
It's much more cinematic and deep with stealth and tactical elements.
The Character customization has been expanded tremendously. You can really create unique characters, whether it be familiy,friends or from TV and movies -- and see them shoot, kill, and possibly die in the field, all under your command.
Procedural generation of levels finally makes an appearance. And it does help. However some areas, especially mission important buildings are somewhat repetitive.
You will be pressed for time. either on the geoscape or on some missions. Some may dislike this, but for me personally it was much more challenging and satisfying.
Cause the game gets better when your well laid plans fall apart and you have to scramble and puts your tactical thinking to the test.
I've had some very memorable moments in this game, ones I wish I had recorded.
This game is a definitely a must have!