Why is this game good?
Well first of all, it's not, if you don't like space the conquest strategy genre......... I mean if you don't, then that's pretty much that.

If you *DO*, then Sins presents you with the unique opportunity to satiate your interstellar meglomania on as big a scale as you want, without being ruined by a clumsy UI, poor tech trees, popcorn-stamina ships, or low fleet caps (I'm looking at you, Hegemonia). For those of us who sat on the edge of our seats for months and months on end waiting for Masters of Orion III to come out, only to be utterly disappointed by the game's poor execution, Sins of a Solar Empire is a thing of beauty.
It's not perfect of course. The scaling shield thing seems counter-intuitive and unnecessarily complex of a mechanic. Ship spam is an issue in some cases, and multiplayer still has some significant issues with it (drops don't count as a loss, no ranking, etc). These are relatively minor to me though, and can easily be corrected with a patch or two. The core of the game, the part that really matters, is of extremely solid craftsmanship, and THAT is what pushes the game's score up so high in my book.
Crappily produced games are a dime a dozen. It's nice to finally find one that I don't have to spend all of my playtime bitching about about its flaws.