2004. Edit: 2005, Feedback doesn't lie. Purchased an AES here on the boards from ckchan.
Was trying to get one for yeaaars before that. My sister and I wanted one to play World Heroes and Super Dodgeball, as we were big fans of the game. Price stopped us. At the same time, my Dad was into coin-op (pinball mostly) and we ended up with a SFII:CE Jamma Cab for several years. However, this was before I really truly understood JAMMA...or had money. We had Mortal Kombat Boards to swap in, but I, for whatever reason, never thought MVS was an option. It was almost traded for a 6 Slot, at my request, but it wouldn't have fit into our basement.
Mostly MVS for me now. Never bought that Dodgeball, though.