Let me first say, In regards to Sins, yes, they should've had a SP campaign. I was disappointed when they didn't. However, the extremely flexible custom map editor saved them from my negative opinions of doom. I spent an hour playing around with the editor, see what functions did what. And then I decided that I could create my own storyline.
For example- 3 races: TEC, Advent, Vasari, on a single star map of 100 planets- I called it the Helios Sector. I set the AI on Hard Random, and wow, was it a huge fight. f'ing epic. I expanded and took half the sector by the time I encountered the Advent. I moved my capital to my frontline base, Hyperia, and fortified the terran planet to the max. 3 repair bays, 3 frig yards, a cap shipyard, and as much gauss and hangar bases as I could stuff into it. It was my citadel- my fortress- my bastion of light shining against the alien horde. The planet itself was a strategic hub- and I knew it would be my objective to take as soon as my scouts discovered it. From there I could launch my assault against the enemy and mantain territorial control.
But the enemy had their own plans. The Advent struck first. I have this feeling the AI knew it's strategic importance-it wasn't a choke point in the map as there was another that they could've used to get around- they could've avoided if they wanted to. No, I think they knew if they could crack that planet my empire would fall. And sure enough, they came.
It was massive. With PSIDAR researched I watched a seamingly endless trail of ships pour through the phase line toward Hyperia. At the moment of attack, my forces were divided into 3 fleets as 1 was ready for the assault, fleet 2 was station 2 jumps away guarding another lane, and fleet 3 was expanding and weeding out rebels, militia, and other scum. When the Battle of Hyperia commenced i was outnumbered 3-1 in the grav well.
The start of the attack I was holding them off as my 2nd fleet was on it's on it's way. The 3rd was a long ways away but I felt I wouldn't need to bring em in. Things looked promising, until the Vasari struck. A wormhole. I foolishly forgot about it and they hit me in my undefended back planets. I desperately redirected my 3rd fleet to stop the vasari but they were outnumbered. The Vasari broke through. Apparently, the Vasari and Advent AI knew I was the biggest threat and they allied because I observed their ships moving through grav wells and not attacking each other. I guess for them, the enemy of my enemy is my friend. not good for me.
The Battle of Hyperia was continuous for over 2 hours and although I was successful at driving them off I paid a heavy cost. I lost 80% of my fleets and so many capships that I lost count. Hyperia was bombed to bits, and I had to re-colonize the planet just to build up the logistical and tactical infastrucure. But nonetheless, my capital was still mine- it had become a personal matter to not let the capital fall.
But even the victory at Hyperia had a bitter taste. The Vasari had taken 3 planets outside of the wormhole and established a foothold. And the victory was shortlived. The Advent re-built up, then returned to Hyperia. But because I had been weakened by the two front war (and the crippled economy due to lost planets) I lost my ground. From there it was a slow battle of retreats as both races continued to take one planet at a time. Near the end, the Vasari offered me a mission- kill 10 Advent ships. I mustered every ship I could to achieve the mission- and I succeeded. The result increased my favorability with the Vasari enough so could offer a cease fire and they accepted! and they were just one jump from my starting planet. Unfortunately, by then the damage was done- my empire was reduced to 10% of what it originally was... and with the Advent pressing for my extermination, I knew it was over- I surrendered.
Total game length: 8 hours.
Now, how's that for a single player experience!? Like I said, the SP experience is only as good as you make it to be.