When done right (alas, I have yet to consistently do it, but I've seen it done), d6 WEG is the best system I've seen for capturing the feel of the game.

Interstellar Wars is a great idea, and I'd even have fun re-examining Heart & Sol, but I've not been able to come up with a good solid story arch to make a good campaign of the former, and I've not yet figured out how to revive the latter in any way that is meaningful. I do regret the last bit, because I know that players had a good time with it. It is unfortunate that the length of time a campaign lasts with me running is inversely proportional to the amount of time and energy I have invested in said game. :-/