For a modern PC gaming sci-fi hero, look no further than Commander Shepard of the Mass Effect series. This guy (or gal) is so tough not even death itself can put him/her down.
I know that Commander Shepard can be played as a bad-ass, but in Mass Effect he/she will still end up being as a hero regardless (except he/she will either be a twisted, sadistic psycho or a no-nonsense cowboy if playing a Renegade character).
Whether you play as a Paragon or a Renegade, what I guess is best about Commander Shepard is that he/she represents humanity and you are the one that role-plays his/her character. So in effect, your set of ideals will end up representing the entire human race, whether it is surprising the aliens by showing humans can be honourable, compassionate, and moral, or demonstrating that even though we're ruthless, our strength lies in getting the job done, no matter the cost (judging by the default start for Mass Effect 2, it would suggest the latter).
The fact that Shepard can demonstrate to us Humanity's strengths and weaknesses would be the reason he/she makes it to #3 in my list of PC Gaming Heroes.