Console emulation on PC is a tried and true tradition, even if emulating anything from the seventh generation onwards has been a struggle. As old as Red Dead Redemption is, getting it to run on an emulator in any stable form hasn't happened in the past, but now an emu called RPCS3 has managed to pull off that feat, if only just.

The problem with seventh gen emulation is that as games become more resource intensive and consoles become more powerful and complex, recreating it all places exponentially more strain on PC hardware, meaning games which are technically less graphically demanding require massive quantities of juice.
The RPCS3 demonstration with Red Dead Redemption and The Last Of Us was recorded on a truly beefy rig. The PC packing a 5 GHz i7 8700K, GTX 1080 G1 Gaming 8GB and 32GB DDR4 3600MHz RAM struggled with these games even though they are years old, and being console games, are by default less demanding than equivalent PC titles.
Running the game alone would be no issue, but replicating the hardware functions of a PlayStation 3 using only software is the tough part.
As such, while the games technically run, they run terribly. With Red Dead Redemption, even the menus look like they run at sub-20 frames per second, whereas actual gameplay dips to single digit FPS.
Texture and effects load in with a delay and colors are sometimes incorrect on top of that framerate issue, so this would hardly pass for an enjoyable gameplay experience, but hey, it's Red Dead Redemption running on a PC.
Emulating a beast as complex as the previous Red Dead game is hardly like trying to emulate a GameBoy Pokémon title, which has been possible for more than a decade now. For its time, Red Dead Redemption looked exceptionally good, the world is filled with all kinds of details meaning a huge number of assets that need rendering, shadows, a ton of visual effects, and the NPCs are governed by a complex AI which further taxes the already heavily laden CPU.
While in its current state, such a level of emulation may not seem like a huge deal, but this achievement is nothing to scoff at. Reliable PS3 emulators are something that emu technology focused communities have been struggling to achieve for years and years, and this marks a significant breakthrough.
Of course, consumer PC hardware needs to get a whole lot stronger, and the emulator software needs possibly inhuman levels of optimization to get things running at a passable 30 FPS, but we're certainly on the right track.
So, who is willing to take a bet on what will happen first - stable emulated Red Dead Redemption on PC, or an official port?