Distant Stars is a good one. But....beware, there be pirates here

Funny you should mention...I pretty much spent the last week checking out the mods and here are some mini reviews:

Distant Stars

https://forums.sinsofasolarempire.com/335474/page/55

Distant Stars is pretty much like Sins enhanced in every aspect - graphics, planet variety, capital ship strength, technology...flavor!  After you play it, you will probably never play regular Sins again, unless you are playing a multiplayer game.  I prefer to play it on bigger maps with slow income settings....fast income settings provide so much money that you won't be able to spend it all if you empire gets to any sort of size.

Here are the 3 most promising full conversions I have played.  None of them are completely finished, but they are all interesting and playable.

Stargate Races Mod

https://forums.sinsofasolarempire.com/314779/page/43

The Stargate Races mod has the Wraith, Ancients, and Asgard currently.  I keep coming back to this mod because playing with each race gives such a unique experience.  Asgard have a few incredibly powerful and advanced ships.  The Wraith have their Hives with tons of darts and lots of support cruisers.  The Asgard have powerful shield techs and mobility.  I'm not 100% certain on balance, but I have played some long games with both Ancient and Wraith, and I found that while each have their challenges, they all have the tools to advance.  On a side note, the biggest Ancient capital ships become godlike in power as they approach level 10 while the Wraith tend to expand very rapidly and out-zerg their opponents, so both races do have their challenges, but I tend to think the Ancients become kind of unstoppable if you survive long enough.  Hats off to Dolynick for this very interesting mod and I can't wait to see other races as they become available.

Star Trek Sacrifice of Angels 2

https://forums.sinsofasolarempire.com/358241/page/66

This is a great mod if you are a Star Trek fan.  It still has some rough edges (automation of some things like repair and shield restore on drydocks isn't working), but shows tremendous potential for when it is completed.  Ship combat is very cool -- the ships behave like Sins fighters making torpedo passes at each other while firing from their various phaser / disrupter banks.  My main observation is that the earliest ships you can make (like the Constitution) are so weak it almost isn't worth building for either scouting or attack purposes.  I played a few games and found I didn't really need to make the early game ships, just went straight to mid game ships.  It would be nice if the progression of the ship technology made every era have its viable heavy cruisers before moving on and unlocking the next cruiser in the progression.  Advanced ships and capital ships are so much tougher than the early ships it isn't funny...  That said, it is still in beta, and if you like Star Trek, this is a very impressive conversion.

Star Wars Requiem

https://forums.sinsofasolarempire.com/344013/page/21

A very polished Star Wars mod....the battles look very much like Star Wars battles with turbo lasers flashing.  A few of the ship powers don't really seem to fit in a Star Wars universe, like the Nanite repair clouds a few ships have...but I suppose this was to make the Rebel & Empire races somewhat competitive with other races that have mobile AoE repair.  While there aren't quite as many exotic "technologies / powers" to use and both Empire & Rebel races seem to play mostly the same way, this mod can't be beat for capturing the flavor of the Star Wars universe. 

The Entrenchment 1.41 version of this mod is still in beta, but there is a link to the mod's standalone webpage, and then go the modders forum and look for the 1.41 beta link.

If someone knows of another great conversion, I'd be interested in trying it out!

There's Bailknight's Graphic Mod:

https://forums.sinsofasolarempire.com/301418/page/1/#replies

Are you kidding?

I played Requiem with a friend just to try it out, and it's about the antithesis of "polished". When a mod lumps every single ship into one weapon type and then leaves the other research trees intact, that's a clue that maybe you might want to work a little bit more on it before release. Save for the models, it needs about six months of solid work to make it a mod worth playing.

Distant Stars is great, even ManSh00ter's dynamic battle mod by itself is great.

ALL of the mods here are good mods. Be it the enhancement mods like Bailknights graphics or Manshooters volumeetric explosion/dynamic movement mods. To the conversion mods like SOA 2, Reqieum, SotGE, Stargate, and B5 mods. TRY THEM ALL, and be your own judge

it is used in Distant Stars Mod which is currently updated

You can download my Volumetric Explosions & Effects mod, since its both updated to the latest version and has most of Bailknight's weapon effect enhancements in it. As I understand it, Bailknights also has Volumetric incorporated so you can go either way, you get pretty much the same deal.

Actually, harpo99999 updated Bailknight's Graphic Mod here, quote:

Sorry for throwing it out like that, but that was honestly all I remember of my experience trying the mod. Since my previous experience was based on an older version, I'll give it another shot and report back with more specific issues.

Nobody's forced to download the mod, but nobody's obligated to withhold criticism of it either. This appears to me to be a subtle variant of the "if you don't like it, make something better" meme, which is inherently ridiculous - while it's certainly beneficial if people contribute, it's not the sort of thing that everybody can do. In fact, it's kind of odd that you don't believe criticism is at least equivalent to actual work - as someone who has been doing this for a very long time, it's much more beneficial for me to get criticism than to have other people work on it with me. "Developer-first" releases of any product tend to be unusable, hacky messes - it's only by getting as much information as possible from a community that you can create a fun end-product.

I disagree. Shared work is sometimes unfinished work, and can lead to lots of issues that haunt you down the road. Anything not created by yourself should be relentlessly gone over. Many projects have specific norms such as texture size and poly count, and mixing and matching meshes for example can lead to performance issues and uneven quality.