>Sonic 3D Blast: Director's Cut
This isn't called "Director's Cut" just as a reference to Sonic Adventure DX: Director's Cut. This hack was actually made by the original director of Sonic 3D Blast, Jon Burton.
First of all, he tweaked the physics. His Youtube channel, Gamehut, gave progress videos on this whole project, and while normally I'd be worried about changing the physics in a game, he showed that this wasn't a slapdash effort. It was thoughtful, and while personally I was okay with the physics before, this is tweaked just slightly enough that fans won't find it weird, but people who didn't like it before have had their complaints listened to.
In the original version of the game, you could get one Chaos Emerald per act. This made it so unless you sucked at the game, you got every Emerald by the first act of the fourth Zone. However, Special Stages are actually tied to Zones, so most players would never see the later Special Stages. If you are any good, you got the Emeralds before then. If you're bad, you probably won't get all the Emeralds anyway. Now this does add a bit of challenge, by forcing you to play the later Special Stages to get the Emeralds, but I think asking you to play every level is a fair addition of challenge.
This hack of course adds Super Sonic, which of course is now unlocked when you get all seven Chaos Emeralds. It's exactly what you expect. He's faster and invulnerable and looks cool and you lose one ring per second. It's just what you want. I could see some people complaining that you can't unlock him until later in the game, since you can't get all the Emeralds until the end of the game, but actually he is still useful, as I'll get to.
Remember the Sonic Tokens you could get in the original? Originally, they only got you free lives, which weren't super difficult to get, so there was no real need to look for them. Now the game actually checks if you got them all, giving you more of a reason to look for them, and thus to explore the level more fully.
Oh yeah, with some things like getting those tokens, or maybe retrying if you fucked up in a Special Stage, you might want to redo a level, but in the original, you'd be fucked. Now there's a very nice looking level select menu between stages. Nothing special, just your Sonic sprite going across a linear line of levels, but it's nothing too dissimilar from, say, the map in Sonic Colors, only linear and of course not as fancy. But it fits perfectly well for a Genesis game. Importantly, this lets you go back to previous levels whenever you want, and shows all your collectables and such.
Each level now also has both a Time Attack and a Score Attack. In Time Attack, you don't have to collect Flickies. So for all the people who hated that, now there's a mode for you. Of course, the game wasn't built for it, so it's not the main mode, but just doing a straight shot to the end is a fun challenge, and the times set felt very fulfilling. Score Attack is what it says on the tin as well. Also pretty fun.
This is a complete improvement over the Genesis version in every way. The only issue is that there's also a Saturn version, and some players may prefer that version. The reason the Genesis version was used was because that was the original, and the Saturn port was done by an outside team. The Saturn port has different textures and music, as well as a different Special Stage actually made by Sonic Team. I do think the textures look nice. The music is also good, though I personally prefer the Genesis version. The Special Stages are good in both, but of course most people would want the fancy true-3D Saturn version.
It would be cool if someone made some sort of ultimate mod that let you choose between the Saturn and Genesis features, and included the Director's Cut features, which could now be applied to the Saturn version stuff. But that's not what we have. Still, Sonic 3D Blast: Director's Cut is exactly what it says, and makes the previous game look unfinished by comparison. Everything about the Director's Cut feels perfectly natural, and it surpasses the Saturn version in every way except for the textures, Special Stages, and arguably the music. Due to the many things it adds, including the ability to go back to previous levels and get more collectables and beat more challenges, I'd recommend it over the Saturn version, and the Genesis version is completely obsolete.