Number 3 in the list is Sins of the Solar Empire and all of the expansions that go with it.
The story is set in a galaxy far far away (not that galaxy!) some time in the future. You play as one of three empires fighting over the planets within. Each empire has their own ships, ranging from the capital ships, which are the big beasts that just blow everything up, to the smaller cruise ships that fill in the bulk of your forces and lets you swam the enemy whilst allowing the capital ships to deal the real damage.
This game has a slow page as it takes time to build up resources in order to get your force together. But once you get going and the planets start to fall it takes a lot to stop you. This long travel time for your forces improves the game so much, the time taken to travel to planets means that your strategy has to allow expansion of your empire, but allows you time to retract your forces if you are attacked.
Another great part of this game occurs when you conquer a planet. Once you are in control you can start to improve it in several ways. One of these options is to explore the planet to find artefacts that improve your ships. Sins also offers a skirmish mode, where you can choose the number of planets and suns that you can conquer. I played a game with over 1000 planets and 50 suns and the game lasted for days. I didn’t play for days on end but it took me over a month to finish, playing a couple of hours a day. This gives the game extreme longevity that can keep you hooked for a long long time.