Since it is unlikely that Red Dead Redemption will ever be ported to the PC, emulation remains the only recourse. The leading PlayStation 3 emulation team behind RPCS3 have made a great deal of progress in making the game playable. In their most recent video, the game runs better than ever before.

Using the emulator allowed ZEROx to record gameplay mostly at 30 FPS. There were occasional drops into the low 20s, but that is to be expected. Even running on an actual PS3, Red Dead Redemption had the tendency to stutter at times. Should a perfect emulation be achieved, framerate drops will still be noticeable.
During the 15 minutes of recorded gameplay, the occasional graphical glitch can be noticed. However, these are relatively few and far between by emulator standards. Aliasing is prominent, but other than that, the emulator brings the authentic visual experience of Red Dead Redemption. You get a bit of blurring, some popping textures, but all of that is to be expected.
Overall, the game is absolutely playable and still manages to look great. It isn't exactly Red Dead Redemption in all its glory, but most of it at least.
There is a bit of a caveat though. As always, emulating newer games is extremely resource intensive since your PC needs to simulate hardware with software. This CPU taxing task can only be carried out at these framerates by the highest-end processor.
Which is to say the Intel Core i9-9900k, to be exact. The newest, strongest processor on the market costs over $500 and isn't what you'd call common hardware. Even if you would build a high-end gaming PC you'd go for a weaker (relatively speaking of course) CPU since the i9-9900k is overkill for gaming under regular circumstances.
If rumors are true, we won't need to wait for the eventual appearance of PS4 emulation to be able to play Red Dead Redemption 2 on PC. After hints were discovered in the game's companion app that point to a PC port, a video was recently leaked online purporting to show footage of the graphical settings the PC version will support. The video looked very convincing, so we have high hopes for an eventual announcement.
The reason why Red Dead Redemption hasn't been ported to the PC all these years in spite of obvious interest isn't known. However, we suspect that it has something to do with the partnership between Sony and Rockstar Games. Beyond timed exclusive content for Red Dead Redemption 2 on the PS4 and a marketing deal, it is possible that RDR being available on the PS Now streaming service precludes it from being ported to PC.
We're eager to see how further optimization of RPCS3 will allow for cheaper CPUs to run Red Dead Redemption this smooth.