I'm surprised no-one yet mentioned it here:

The developer of the late "arcadeshop Multi board" has developed a brand new board that is now available through
www.Phoenixarcade.comAlthough this is "another" emulation board, it is in NO way comparable to the Chinese xx-in-1 boards available.
In every way possible they are better.
Here's a full list of features:
- 2 Gigabyte SD Card capacity for hundreds of games (sold separately)
· MP3 Jukebox Game (similar to Guitar Hero) plays back MP3 files from SD Card
· Quarterly projected (but not guaranteed) firmware updates (January, April, July, October)
· All high scores saved on SD Card and retained when game turned off
· Supports both VGA and CGA monitors (CRT or LCD)
· Supports standard 8-way joysticks, Happ style trackball, and Happ/Midway 49-way joystick controls
· 49-way joystick automatically translated to 4-way, 8-way, and diagonal-only sticks
· Lightgun control input supported for gun games
· Supports either amplified JAMMA mono speaker output, or line level pre-amp output for stereo sound
· Animated game icon menu navigation for quick game selection
· Access to all game and cabinet settings through PC setup application and on-screen menu
· SD Card stores statistics of games played, time played, coin counts, etc.
· Entire collection (as of 9/1/11) of upright and horizontal games fits on a single SD card
· Switch between upright / cocktail / horizontal mode from onscreen menu
· Purchased games unlocked by Serial Number, no codes to remember
· Small footprint 3.5" x 4.5"
· Dynamic menu system is automatically built with the games you load/select
· Animated menu with icons and game marquees
· Enable or disable games from menu
· Game variations (faster speed, auto fire, etc.) available from Game Options menu
· Optionally disable panel controls until coins are inserted
· All control axis/directions can be changed in setup (no need to re-wire your trackball unit)
· Arcade and free play modes
· All credits are global and can be shared between different games
· On screen configuration/setup menu
· Built in, on screen hardware diagnostics (tests video, audio, inputs, coin counters, LEDs, etc.)
· Test mode button on board (JAMMA harness "test" input also supported)
· CGA/VGA mode selection button on board
· PCB only requires +5 V.D.C. power (uses less than 1A at full volume)
· Software controlled volume adjustment
· Field programmable by the end user
· Built in two-channel lamp/LED driver (use for Atari 'cone button' lights & buttons, etc.)
· 30 Day manufacturer warranty covering manufacturing/parts defects (see warranty for details)