It's probably one of the best RTS ever maid. I have looked and haven't found space strategy game better than Homeworld
Whenever I want to play a good RTS which include space ships stars, big explosions , I reach for Homeworld :)
What's most important game is quite old by now, but still kicks , graphic is very good ( as for game created 7 years ago).
As for gameplay it's very god. Learning curve is quite simple. You just start , play a while and sudenly you you can do all, and universe has no secrets before you :)
Tech tree is not to complicated. You can focus on one branch and develop it first ( for example battle-cruisers ) but then enemy will crush you with upgraded small fighters, bombers and frigates.
Also gathering resources is solved very good. Most of the times asteroids are big, so you don't have to worry about switching gather places to often. Of course to win you have occupy as many gather spots as it's possible for bigger cash income
Too bad they didn't created Homeworld 3 by now. I would definitely buy this one :)