Oldest game you still play

For me, it's Steambot Chronicles. It is a wonderful JRPG which I consider as a hidden gem as it was really ahead of its time. It featured so many gameplay mechanics which was really cool. You can play billiards, you can play the stock market, you can fight in a mecha-bot battle arena, you can play different musical instruments, you can have a band and you have choices in every player decision which was really great. It's my all-time favorite PS2 video game.