Oh it's PR guys. I'd probably guess that almost everyone who has had hardware in the gaming industry would claim the same thing. You want your PR guys to say this. It's your old-fashioned political argument of "I was the first to say this" or "I backed it before everyone else". Don't know why people would get angry at that. I expect them and the others to do it. There's a reason companies always boast how long they have been in the industry and how much total unit sales they have accomplished. It's good PR.
As for the truth of it, can't deny that Sony really had some big systems with PS1 and PS2. But you also can't deny that the American and Japanese markets had not only been well established but well "legitimized" as Sony would put it. I don't think they could make a case for that. Mario was a household name and even Sonic from Sega was very well known along with other hosts of franchises. Not to mention PC gaming and arcade gaming was big all around both areas. Gaming was seen as a form of entertainment and pretty mainstream. Playstation and Sony just fed off of it like other contenders to come such as MS. Really I don't think we see any knew expansion in these areas until Wii/DS/iPhone gen which is rather obvious now. Hell the way people describe those systems, for better or worse, pretty much says they agree haha.
Obviously though, an argument could be made for the European and definitely the Asian markets. I would say what they did more was establishment as they were a bigger company with more resources than Nintendo, Atari, or Sega. As for legitimizing in the European market, it is always tough to say. Gameboy was getting big there. Arcade and PC gaming were both taking off. Really, all at around the same time, due to the end of the Cold War. And then when we move after that, PS2 and DS along with heavy push from PC gaming really marked the next era. I guess if we wanted to say the console push, then definitely Sony, but obviously there is more to the market (especially in Europe) than console gaming. Asian market and Oceania, I don't think there is too much contention that Sony was the big player and really helped to open it up. Along with help from PC gaming, it really was the big factor.
So that's my take, but remember this is just PR. Sony has been a big player in the industry and did a lot for the industry in getting more gamers to play and combining entertainment functions as they said. But don't buy into PR by any side. For the industry to get where it is right now, it took the works of all the major players from the start to the recent. I'm just glad they got it here and for many people around the world as I personally like gaming. As long as they all continue to do their part, then I'm happy.