I personally think that rebellion's first AvP is the only good one. AvP2 and the recent AvP are too cartoony for the Alien setting.
But they are very far from being RPGs.
Adventure games could be closer, if you want to try the star trek point and cluck (Judgement rites, 25th anniversary, etc).
there was also oldies like B.A T. and Chaos in andromeda (that was on the Amiga), or even Battletech: the crescent hawk's inception, available on PC.
And FTL should come soon...
HectorOfTroy: Thanks for your suggestions guys. I have played Mass Effect and I love it. I have X3 and Space Rangers so I don't really need spaceship based RPGs.
Can anyone recommend a Sci-Fi RPG similar in playstyle to Baldur Gate (similar to SW KOTOR)? Anything on GoG?
I haven't played it, but indeed Anachronox is very much praised on GOG. And I'll probably buy it sone day. I would, if I was looking for the ame sort of game as you right now...