Hmm, I think to deserve the label of "one of the best" you need to appeal to a very large audience. For me it was certainly one of the best, if not the actual best - I struggle to think of a scifi film that I thought was better. Scifi has so many subgenres....Serenity has a huge amount of nostalgia attached to it but it really wasn't as good as Firefly. The Dark Knight was also incredible, but here it's apples and oranges.
Anyway.
I adored the "first contact" scenes...and I loved that the point of the first contact was, in a sense, to force an intra-species first contact of sorts. What if the most unknown sapient beings in the universe to us live on the same planet as ourselves? kinda deal. I would go with octopi in that premise, but having it be countries we're not allied with is an even cooler take.
As for the daughter plot - ehh, it was fine. Made the story more personal. I thought the romance was fine, because it gave some clues so you could figure out who the father was and what is going on with the timeline. "Ask your father, he's the scientist," etc.
But if you're going with "one of the best scifi movies" I think you have to qualify it as like, "one of the best intellectual scifi moves." Because "scifi" has really come more to mean either (a) superheroes or (b) space opera when it comes to movies, imo. If I hear "scifi" with zero qualifications I'm expecting Marvel or Star Trek/Wars.