Honestly, I wouldn't shed a tear if Sony left the console business and never came back. I was never a fan of Sony's games even during their prime - I just don't like the cinema/dialouge heavy games they seem to pride themselves on. But in the last 5 years or so they seem to have done everything in their power to tarnish their image, from the rootkit scandal, to the axing of lipsang, to 599USD, and the removal of BC from the PS3. And the Move was just the final nail in the coffin for me.

Now MS, I don't exactly like them either, but I do like the Xbox 360, so they can stay.

Also, I would LOVE to see Sega come back, although the quality of some of their games has taken a slide as of late.

Sony, for their arrogance, and for continually dismissing Nintendo, while they copy the Wii Remote. At least Microsoft tried something new.

No one.  Competition is a good thing and a lack of it promotes complacency.

Edit: gah , i think i violated my own rules on this one, just ignore and move on.

Sony, to have help Sega to be sure they can't put their head out of the water (they announcement of PS2 just when the dreamcast was out to be sure the owner of the ps1 don't buy the dreamcast even if it was much better line up at launch than the ps2) and for the "aggressive" business and bad PR they bring in gaming (plus the competition bashing... Motion is a fad, before copying it).

If I had to choose one it would probably be Microsoft. Keep in mind this applies to console gaming only. Following are the things that I personally dislike that Microsoft has done (does):

1. Pay to play online. Kudos to Microsoft for building a great online infrastructure but did they have to go D-bag on us and make us pay to play a sizable portion of the games we just purchased?

2. I don't have empirical evidence but I feel like they have killed the single player, or campaign portion of gaming. Everything has become multiplayer or bust and I dislike that. I attribute that to the push for online in EVERYTHING. I enjoy a good multiplayer game but not at the expense of the single player experience. Every game does not need multiplayer or even online options.

3. Don't know if they started this, (maybe a different thread would be appropriate) but micro-transactions and downloadable content. I think at the very least they were at the forefront pushing this. Game companies selling us a full priced game that is purposely lacking content so that they can release it mere weeks afterward for $10-$15 is wrong! I'm aware that was probably a run-on sentence. If the release of the downloadable content were a couple of months from the release it would at least seem like developers had to have the extra time to develop it.

4. Unreliable hardware. Do I need to explain?

5. Releasing a machine that focuses on online connectivity that lacks built in Wi-Fi. I know they've now corrected that, but for most of the installed base it was a $70 add-on.

6. Shooters, shooters, shooters. I know, probably isn't entirely Microsoft's fault but they are oh so prevalent on their consoles. Heck, practically built the original Xbox.

Well, that's all that I can think of off the top of my head. Oh, and I think Microsoft tries way to hard to be cool and edgy. Even their very name with the "X" was a trendy, "Look at us we are EXTREME!" move. Nintendo's press conferences are often not the most exciting (for non-Nintendo fans) but at least they have charm.

To put it another way, a rival is someone working towards the same goal, whereas Sony is more like an enemy - fighting AGAINST Nintendo, rather than towards the same goal. Think of the difference in Pokemon Red/Blue/Green, you have the rival and then you have Team Rocket. Sony (and Microsoft) are more like Team Rocket admins. Note that I'm not saying that Sony or MS are evil, just that their goals are different.

As for my own answer to the question - as odd as it sounds, my answer is Activision and EA. While they're not strictly in the "console race", they have such strong hands in the development of all major consoles, and in my opinion, those hands are why the industry is so screwed up right now. If console makers made their consoles with an eye to the consumer, rather than to the huge 3rd party developers, it would be better for everyone. And this is why I prefer Nintendo over the other two - Nintendo clearly puts the consumer ahead of the 3rd parties.

I want Sony to be out. I can't stand their PR practices, their bragging when they are doing poorly this gen, their horrible arrogance, their suppose superiority in technology when everything they release is utter crap, and their unoriginality

They're all going for the same goal , Money.

Rivaly in anything is what keeps it alive.