>>11970884
tenhou.net for PC
Yakuman for the Game Boy for a 2-player mahjong variant. There was also a NGE version for the GBC that even had cutscenes and shit. Haven't played any regular 4-player Riichi Mahjong games other than the minigames in Yakuza, it's in Yakuza 2 for PS2 though so technically retro.