FPGA

Check this... 

Pick all those bunch of old computers, shake it all together along with some new add-ons such as modern  mouse and keyboard connections,  VGA, SD or Compact Flash cards... what you get?

These are only two examples: MSX 2 and Amiga running on the same hardware. It is not emulation. It is the hardware reconfigured to be a MSX or an Amiga. And, it can be reconfigured to behave as a TRS-80 Color, Spectrum, Commodore 64 ... name it!

Are you new on this, and need some directions? Look for these words:

        Altera, Xilinx, DE1 Development Board, Spartan 3E Starter kit, FPGA, VHDL, Verilog,  Reconfigurable Computer, opencores.org... from there, you will get much more.

I have got these boards:

        Altera DE1 Development Board

        Xilinx Spartan 3E Starter Kit

        Charmedlabs Xport 2.0 + Gameboy Advanced

        8bitbaby pcb + Altera MAx3000A EPM 3064 CPLD

And these ready-to-use systems on a Joystick:

    Commodore C64 CDTV with 30 games inside

    TV game Namco (MS Pacman, Pole Position, Galaga, Xevious, Mappy)

    TV Game Namco (Pac Man,  Rally-X, Dig-Dug, Bosconian, Galaxian)

    TV Game Activison (Atari Games, including Pitfall and others)

    TV Game Atari (10's of games, including River Raid and others)

These are the list of retro machines I were able to run on my boards:

    MSX 2

    Amiga

    TRS-80

    Commodore 64

    Vic-20

    Vector 06

And the following arcades: 

    Invaders

    Pac Man

And there are more. People around the world have done a nice job, and recreated several old systems using modern technology. Just search for them. Or better... recreate yourself the machines you miss from the good old times! FPGA technology are very suitable for this purpose.

Of course, you must learn how to reconfigure the hardware. Looks terrible, but it is, in fact, not very complex. You must learn a new "language", VHDL or Verilog are the most common. Look in my links for places where to start.