- Play native Windows games (Win 95/98 to present)
Yes and no. Some (or many, no idea) Win95/98 games are not compatible with Windows 10 but most WinXP games will run flawlessly.
- Play DOS games (natively, through DOSBox, or GOG)
Not a Windows strength, as that works with any other DOSBox port as well (Linux, Android, etc.)
Win10 doesn't have a DOS included anymore (command line is not DOS), so I doubt you'll get DOS games to run natively.
GOG usually uses DOSBox as well, I'm playing many GOG games on the Pandora
- Play Linux games (install a distro)
If a distro can be easily installed. It probably will be, but we don't know yet.
Also, depending on what hardware is included, you might have issues with the drivers (capacitive touchscreen, Wifi, etc.)
- Play Android games (AMIDuOS, Genymotion, BlueStacks)
Yes and no. Simple Apps will run natively (Java), all games using C++ code have to be emulated, so speed might be good or not.
I don't know about compatibility with games, but from what I read, it's somewhat basic right now but will be improved in the future.
- Play retro games (x86 has the widest and most mature selection of emulators, from Amiga to ZX Spectrum)
Not sure about that.
What emulator is there on Windows that you're missing on Android / Linux?
I don't know of any system that's being emulated on Windows that's not available for ARM as well.
- Play Flash games on Kongregate, etc.
My Pandora can play Flash games with a dedicated flash player fine as well. Yes, the flash player is a bit older, but so are most flash games as newer games are usually coded in HTML5
I'm sure there's also similar players for Android (though I haven't looked, I'm not into Flash games)
- Stream Steam games if it runs too slow
- Stream Xbox One/360 games (like the Linx Vision)
- Stream PS4 games (soon to be available)
This heavily depends on the Wifi chip that's included.
It could very well be it's not fast enough (mobile Wifi chips usually aren't the best ones).
A portable Windows gaming machine with at least 1024 x 768 resolution and 7-inch screen would be very high on my "to buy" list ^^.
7-inch? That's basically a netbook with an external controller ;)
So yes, Windows has its advantages, but not many of the ones you mentioned are exclusive.
Solutions for those exist for Android and Linux as well.
The Pyra Devboard can also run many classic and even some not-so-old Windows games through WINE and ExaGear (i.e. stuff like Diablo 2 runs without any issues).
Yes. it's a workaround using a software, but so is running Android Apps on Windows :)
So it depends what your focus is. :)