I agree. Competition is what drives companies, people, etc. to do better, to produce a better product, etc. I think that there are strong points for each game company. Nintendo excels at games for children and everyone. They have some amazing franchises like Mario, Zelda, etc. that can't be touched. They aren't as concerned with graphics and aren't looking for the hardcore gamer, but I still continue to buy Nintendo products for some of the amazingly fun games that they have. I could play Professor Layton and Phoenix Wright all day and can't really think of a Sony or Microsoft product quite similar and as well produced.
Sony is definitely Microsoft's most direct competitor, but some of their exclusive titles kick butt (Uncharted being one of my favs) and Sony has always had a place in my family room throughout the years, especially before the Xbox consoles had come out.
PC gaming has been around for a loooong time and I think it's gaining a wider spread of fans again. For a while PC gaming was around, but seemed to be more WoW and other hardcore gaming (lots of MMOs, crazy amazing home built rigs, etc.) but I think that Steam has been doing a great job of bringing some more fans to PC gaming.
Then there is Xbox. Which is working to be an all in one entertainment/media device and has tons of great exclusive games and unique hardware (Kinect anyone?)
Without all of the competition to sell the most systems, come out with the next Halo (which is Titanfall IMO) or the next amazing piece of hardware (possibly Occulus Rift?), etc. I don't think we would have nearly as many of the amazing games/products that we do in the gaming industry at the moment.
End of looong jumble of thoughts.