PC Engine.
Not only does it look like a prop from the set of TNG, but it is delightfully tiny. The cartridges are little cards that you slot in the front. There is literally nothing bad about a PC Engine. (Except for maybe that it's only got one controller port)
The PC Engine/Turbagragix 16 also had a handheld (PC Engine GT/TurboExpress) that was way ahead of its time. It had the same power as the home console, was color, had a backlit display, and even had a TV tuner attachment. And it was released in 1990. The Sega Nomad basically copied these features in 1995, and Nintendo didn't have a colored, backlit handheld until 1998.