The points are all true. And I liked Aliens 3--I caught it when it first came out on video (I was too young to watch it in theatres at the time), so the crap CGI never bothered me. I saw it again when I was older, and yeah the CGI was bad, but the movie was still good.
But.
The only way that Alien 3 was a major standout from Alien and Aliens was its depth. And character depth was never the driving force behind the concept of the franchise. The alien is the title character. The alien is the star. The alien is what we all came to see. And there's no denying that their decision to use CGI (which, in the pre Jurassic Park era, most of the time made everything look like the goddamn Lawnmower Man) made the star of both previous movies look like shit.
In a sense, it's a fate worse than death by violent chest-birthing; at least the dead colonists were mangled with a sense of meaning, not because some producer jumped on the "CGI does it better for cheaper" bandwagon WAY too early.
Now, you could argue that each movie takes a completely different approach, and you wouldn't be wrong: Alien was essentially just a schlocky sci-fi horror movie, Aliens was a sci-fi action flick, Alien 3 went back to the horror angle but re-did it with more depth of character, and Resurrection was a failed first-attempt at a 'space cowboys meet prodigal woman who the higher powers have been experimenting on' concept that eventually turned into Firefly.
No, you wouldn't be wrong about the different themes. But all the films were called Alien. All the films featured members of the same family--Paw Alien in the first one, Ma Alien in the second, the Aliens' dog Old Yeller in the third, and the Aliens' freakshow cousin who's the product of severe inbreeding in the fourth. And fucking up the alien in an Alien movie is like fucking up the meat in a hamburger: Yes, you could scrape off a patty that's been way over-cooked to mask the fact that it's been off for about two days, and the rest of it might be an otherwise quality sandwich--but it's not a friggin' burger anymore, is it?
So yes. Good movie. Not the best.