I couldn't really elaborate earlier because I was on lunch break with my phone, but I think Aliens did a pretty good job of opening up the Alien universe. The corporation only really hinted at in the first one is brought to the forefront of the second, you see more of the Alien hierarchy, you see more of the colonial life and government, you see multiple locations, technologies, and demographics of the population, future military technology etc.
Now all the EU that focused SOLELY on the same aspects over and over again can be blamed on being close minded for sure, but I feel that Aliens had a pretty big scope that was obviously laying the groundwork for something more grand and bigger scale before Alien 3 happened and went the way it did.
Which you could have still done something with, the series didn't need the Ripley character anymore, until they decided that the series needed the Ripley character and basically eliminated 200 years post Alien 3 to do anything in.
The EU HAS been much better lately, but I contain that stuff in its own continuity after Hicks and Newt became Wilks and Billie. If it happend once it can happen again.
Kind of like how WY won and has a xeno weapons program, only they went bankrupt in Alien Res and were bought out by wal mart. I always took it as the implication being that they wasted too much money trying to locate and exploit the alien and bankrupted themselves.
Anyways, side tangent.
Besides, Scott tried to reopen the universe with his two prequels and all their crazy shit, and we all saw how that went down.