Original Midway Pac-Man on MAME is best, IMO. It's by definition the most "original, authentic" way to play the game.
But if MAME stymies you, or if you're looking for the best version to play on a 480i CRT, I recommend the NES port (either Tengen or Namco, they're functionally identical). It doesn't have accurate colors (what arcade port does with NES's weird palette?), but the arcade action is 100% there.