i've noticed the running theme with every system on this thread: cancelled before it even got off of the ground.
the jaguar, saturn, dreamcast, vita, wiiu. all had potential, but for one reason or another, all of them failed.
i haven't played some of the older systems, but the vita had cross connectivity with the ps3/4. game selection was limited, but playing shadow of the colossus with the vita as the controller was pretty cool.
and playing disgaea 3 on there was amazing. quick load times and more content.
the wii u gamepad being a second screen or map display is awesome. you could play batman - arkham city, bayonetta 1+2 and pikmin 3 while watching ed, edd, and eddy.
the dreamcast had awesome games like skies of arcadia. i have the gamecube version, and i was looking for a copy of the dreamcast version when i still had one of those. no matter how many times i come back to that game, it still feels like the first time that i am playing it. only minecraft and botw have gotten close to that feeling for me.
i'm pretty sure even the game systems that had a lot of coverage and exposure are still far from being completely pushed to their full capabilities. i saw a guy on youtube who's still checking out everything that the n64 can do. here's a video by him on the n64's cache system:
it'll take years to fully understand each and every system and its full potential.