There should be plenty of info available if you search for it, but I'll sum it up: Purists usually seem to cringe over multis, but they are undoubtedly a crowd pleaser -- your typical houseguests who stop by to play some games will likely flock to the multigame and ignore any other dedicated games. I love my multi and admittedly play it more than all my other games combined.
Not sure if they're still available anywhere, but the slickest one that I've used is the Arcadeshop multigame. Nice interface and works well. The typical iCade 60-1 is a bit cheaper, but it's decent and has trackball support. It is not without its quirks. Be aware that if your multigame has Centipede, Millipede, and Arkanoid but lacks trackball support, those games will pretty much be unplayable with the joystick.