Concise article from Korg about their own history , a company founded by Tsutomu Katoh who got his start making some accompaniment devices. They evolved quickly into one of the premier synth companies as well as producing various other gadgets of interest. Here are the "40 years of gear" articles from Sound on Sound magazine. part 1 part 2 part 3
Also see Joseph River's Timelin at Keyboard Museum

Products: (In near chronological order)

700 700S 800DV PS-900 770 PE1000 PE2000 M-500 micro-preset PS series MS10 MS20 MS50 VC10 PS3200 CX3 Sigma Delta Lambda Trident LP-10 Mono/Poly PolySix Poly61/M Poly800/EX800/II DW6000 DW8000/EX8000 DSS-1/DSM-1 DS8 M1/M3R T Series Wavestation 01/W/FD/R 03/RW X3/05RW i-3 Series Prophecy Trinity X5/X5D N Series Z1 Triton Series Karma MS2000 M3

Korg's contribution to the market as I think about it would seem heavily towards the side of giving people more for their money. The PolySix and Poly800 products being prime examples. Their products seemed to shadow other people's innovations slightly but the price was much less. I guess they and Roland just happened to enter the market about the same time with products that were quite similar in overall design; probably in response to the ARP Pro-soloist. The later 900PS was more similar to the Conn Electric Band which definitely 'borrowed' some ideas from the Pro-soloist. The PS series appear to be a merger of ideas from the polymoog and modulars. And of course the MS mini modulars.
But anyway on down the line we see the Lambda which improved on the Yamaha SS30 basically. The Delta which improved on other polyphonic/synth mix machines and Sigma which I guess had maybe more uniqe features. But it took til '81 for them to come out with a polyponic synth that was affordable in the polysix. Then the poly61 and poly800 which really broke the price (and size!) barrier. The DSS-1, while not a great commercial success...still undercut the competition again in samplers, and the M1 taking the workstation concept to a new level, the Wavestation borrowing Dave Smith who had just finished the SY22 for Yamaha to make a better machine again of the same nature! Need I go on? Nothing overly original, just..better...and cheaper! Wait a year or two until technology matures. Let the other companies pay the price for pioneering. In his early days the owner of the company poured a lot of his own money into it so perhaps he learned this lesson then. :-) It appears to have been a good move. Korg has produced some of the most useful music machines on the planet. And they appear to be about the most prolific if not the most in terms of recognized synth products.