It's considered a strange fluke of luck that Ripley's shuttle was actually discovered, and it might have gone flying through the universe forever, with Ripley still asleep. However, it is *because* the shuttle is discovered that every character in the movie (and possibly the next two) that dies meets their fate. After all, it's not explicitly spoken but strongly implied that Burke is responsible for the colonists exploring the alien wreck because he wanted them to be impregnated so that he could somehow... make a profit from the R&D? Burke also knows of the alien wreckage only because Ripley told him the story. So, the colonists had lived on the planet for 20 or so years without a problem until Ripley's shuttle is discovered and she told the suits about the alien presence on the planet. It might have been better for all involved for her to have never been rescued...
Although I doubt Weyland-Yutani failed to notice that the team they sent to investigate a crashed Alien ship vanished without a trace...
It's quite possible that the W-Y execs who sent the Nostromo out in the first place buried the records after an expensive ship and its crew failed to report back. Meaning the company as a whole did in fact forget about the whole thing. The Fridge Horror there is that the company doesn't even remember what it did to Ripley and the Nostromo.
It's also quite likely that Burke didn't believe Ripley's story (or thought it was exaggerated), and that he sent the colonists to check that particular grid coordinate just to verify that there was nothing there - not as part of a nefarious plot to have the colonists impregnated.
The point is that Burke wouldn't have sent the team to investigate the crashed Alien ship if Ripley hadn't been found.
Whether Ripley was found or not the Aliens would still be there and the company was still terraforming the planet. The longer the ship went undiscovered the larger the civillian population would be and the larger the casualties would be when it was finally found. The really horrifying thing is that the movie is one of the better scenarios for how things could have gone down.
The heartwarming exchange of first names between Ripley and Hicks - it was the last time they ever spoke to each other. If you take the third film as canon however.
Though she's certainly the one most human audiences would root for, Ripley is not the only Mama Bear in the film, since the Alien Queen holds back when Ripley is only threatening the eggs, then pursues after Ripley decides to torch them (as the eggs start to open, meaning she and Newt were dangerously close to getting facehugged by them; if not for that, it almost seems like the two might've gotten away with less incident). Ripley also causes her ovipositor to be ripped off, which even aside from the physical pain is a very, very personal kind of injury (assuming of course that the xenomorphs value that kind of thing the way most intelligent creatures would)- is it even possible for that part to grow back? For that matter, Ripley herself was only lost for so long (and thus separated from her own daughter for the rest of her life) due to the first incident with the xenomorph onboard the Nostromo, so there's sort of a revenge cycle to the whole thing too. So although the alien queen is responsible for the slaughter and consumption of quite a lot of humans, it could still be said there's some tragedy on both sides of the situation- as Ripley herself put it (albeit directed mainly at Burke's cruel behavior), "I'm not sure which species is worse".
Ripley was clearly running on a burning, hateful desire to get some payback from the creatures. Which is indeed tragic, because had she accepted the Queen's offering to leave, the Xenos were just scant minutes from being vaporized anyway, and all the events in the sequel would have been avoided. Of course, one can hardly blame her from acting out on such emotions, because seriously, screw the Xenomorphs.
It is quite likely that Ripley did intend to just leave. She was just backing away, and it wasn't until one of the eggs she was passing opened that Ripley gave the queen a look that said, "Bitch, please!" and opened up a can of whoop-arse on the egg chamber. So really, the queen brought Ripley's wrath down upon herself. If she'd just let Ripley leave, she could have lived happily ever after. (Well, until she got a nuclear explosion in the face...)
The addition of the Ripley's daughter subplot adds in a small bit of Fridge Brilliance. Ripley is the only one who's able to get anything out of Newt when she's first found. Of course a mother would be better than the marines at getting information out of an uncooperative child.
Once she starts talking, Ripley's also the only person to listen to Newt who ends up being a mine of tactical information. The Marines were either too arrogant or (later) panicked to recognise the value of a survivor, something Ripley immediately seizes upon.
Their plots mirror each other: Ripley's a mother looking for a daughter, and Newt's a daughter looking for a mother. Hence the reason Newt calls Ripley "Mommy" upon beating the Xenomorph Queen.
Newt's knowledge of the air vents and where they lead to make a lot more sense with the additional scene with her family. She says "all the kids play there" which implies it's a regular thing. She's also likely had a lot of extra practice travelling through them since the aliens started attacking.
In the novelization and the director's cut, she and the other kids play Hide and Seek in them, which she's champion at since she's small enough to fit in places no-one else can.
Why Hicks was out of commission even though he was only burned by the acid? Because he breathed in some of the fumes of the burning. His lungs were being burned on the inside.
Near the end of the first movie, Ripley is trying to flee the Nostromo and an automated self destruct countdown voice can be omnipresently heard. This time, she's *running back in* during an automated self destruct countdown voice, and might very well be noticing that when she's in the elevator on the way back down.