Steam and Valve have pretty big muscles in terms of being a video game distribution and hosting platform – which is awesome for me, being a Debian "Jessie" backports user, which SteamOS is built on. Every game on Steam listed as being SteamOS/Linux compatible that I've tried, even if it lists Ubuntu as a requirement, has worked flawlessly for me. Anyway, that being said, they still don't have the same level of muscle or at least entrenchment as Windows in the world of gaming, and more importantly to devs, game sales. Fortunately for Valve, they sell games for Windows.
Other than the NES, I'm not a console user. If I were I would go with a Steam Machine, or more likely, a Steam Machine I built myself, of course. There really is no need to for me though, since I have my main PC hooked up to my TV as it is anyway. I mean, I could even just use a laptop wireless and hook it up to my TV and use it as a console. In theory, consoles really shouldn't even be relevant anymore, except of course for their existing entrenchment and continued push by the higher ups, and very importantly, their ease of use. People don't have to figure out anything beyond plugging them in or using them over Wi-Fi.
Steam Machines are one half of one dichotomy and another half of a different one, which unfortunately doesn't really add up to a whole. As a Linux user, it would be awesome if they took off, but they're solving a problem that doesn't really exist. I mean, I was hooking my PCs up to TVs even back in the very early 2000s/late '90s.
I have a suspicion that some of the very high ups at Microsoft and Sony wouldn't really even mind if PCs (as we know them now) went away altogether, so they could just sell us their proprietary walled garden boxes. Windows 10 (and before it 8 and 8.1) and especially DirectX 12 are a measured incremental move in that direction. In the short term, this is probably even a good thing for some gamers and users who aren't as computer savvy. In the long term though, I think this limits choice and really even capability and innovation. I can understand if some might take this as being hyperbole, but from my experience it really isn't. Working with radio gear and electronics hardware on a design level, it becomes painfully obvious just how intentionally crippled some things are to maintain the relevance and value of intellectual properties to those who have an invested interest in their continued proliferation. I mean, we even see the same thing in regards to the implementation of encryption technology (security) on the hardware level.
I'd love to go into some of the specifics of the amazing things current electronics hardware and firmware are capable of – I'm talking about an order of magnitude better efficiency or capability in some cases – but that's getting too far off topic.