While those involved in the game have done great things, particularly making a game that many computers can play, not lying about its requirements/specs and not requiring the buyer to be online or have limited installations (and all that DRM nonsense), what you've discussed is part of the problem for this game and its sisters.
The problem being that it's all a bit empty and unchanged. By that I mean the game says "here's some planets and, some obligatory factions.. well go on then...". No story, nothing to work towards (arguably bar a tech tree) and while the numbers are different depending how we set it up, if it isn't incredibly similar to the last campaign, it'll be like the one before it.
Some games do do this open-ended style, some strategy games, but they're incredibly in-depth so there was no need for, or possibly point to, a story arch or missions. The reason certain successful games (usually made by a guy called Sid Meier) use this and don't suffer for it is because the dept means you're living your own story, and the variety and options can mean a different story a lot of the time. Play Alpha Centauri once, and you'll find yourself in World War I. Play it again, and you'll be finding yourself on a journey to learning the planet's origins and ecology. Play it again and you might be finding yourself in a political game and shaping the planet as you see fit physically. One more time and you might have some 'super-alliance saving the world with nukes' story going on.
The similarities in this game go further. I also own Galactic Civilisations 2 due to rave reviews, and was left a bit disappointed. It's not bad particularly, it just got boring and samey after a few levels. When I got this game, I found it was very similar. The battles are obviously more advanced, but that's not to say it is advanced, though. Mainly though, a lot of things I did in one game, I did in the other.
My final gripe would be the 'meh' backgrounds. Pretty, yes, but there's only a few, and it's started to become a gripe of mine that sometimes in games (Homeworld and one of the sectors in Freelancer come to mind) space will just look like a sky, using the excuse that being closer to the center of the galazy will cause sky-blue space or even 'clouds' (surely it doesn't?).
I suppose Civilization is the archetypal strategy game that all others will inevitably be compared to. I think sins offers something new to the genre as is certainly a much better offering than civilization 5 (which was a massive disappointment in my view). I think some of your criticisms are a little on the unfair side. Sins is a space strategy game with a heavy reliance on tactical battles. Its not a god type game like populous. I guess the distinction comes down to whether you are the type of player who likes table top battles with a heavy reliance on tactics (think of risk, but for computer games); or whether you are the type of player who likes god games where you build yourself a civilization, construct structures/wonders, and basically write your own story (with less of a reliance on combat). It would be a hard thing to achieve to combine both of them successfully, and to my knowledge alpha centurai (as you rightly point out) is the only one to come close, but even that isnt perfect. I think that developers would do better to just concentrate on one type of game and make it the best they possibly can. Once you start flirting with both styles then inevitably the game will be poorer as a result (civilization 5 is a case in point).
[quote who="Ozzy38" reply="123" id="2945628"Modding can be a dangerous workaround. I wouldn't want PC games to start being released with a base, and expect regular people to make it valuable with modding.[/quote]
Unfortunately that tends to be the case nowadays. Modding ought to be a way of enhancing games, not making them into something decent or playable. There are few strategy games around where modding has not come to the fore. I guess that is a result of rigorous playtesting by thousands of people, not just a handful. I point again to civilization 5, which will need some serious modding in order to make it a decent game.