For instance, the "Blade Runner Blues" patch as I understand it is actually one of the brass presets on the Yamaha CS-80. (Bad recording but here: https://www.firsthomebank.com/personal-banking/deposit-produ...) The CS-80 has a pretty unique architecture for a polyphonic analog. (http://www.cs80.com/tour.html) To get a patch exactly right would require replicating layout, filter architecture and structure, etc.
Knowing basics synthesis, however, can get you pretty close. I have a patch on my Alesis Andromeda (which has some CS-80 type elements such as a ribbon controller, dual resonant filters, and an unfiltered sine that goes to the post-filter mix) that someone did in a user community -- it came out decently good. I was able to Google a book page that gives a good overview of recreating it on other synths. (https://books.google.com/books?id=Jz1JMnZNO88C&pg=PA74&lpg=P...)
Now, to really get the Vangelis Blade Runner type effect, you have to be able to play a synthesizer expressively. This is unfortunately is tougher on most synths compared to the CS-80, due to the CS-80's polyphonic aftertouch that most synths lack. That being said, there are other techniques people could do. I understand that Vangelis used pedals to manipulate filter and volume, and that is something that can be done on many synths that I don't see a lot of people taking advantage of. Don't discount playing technique when it comes to the art of sound design, in other words.