Not sure how old you mean. If you like online multiplayer games and WWII FPS games, Battlefield 1942 is excellent. It's not exactly a simulator, but it is more realistic than MOHAA, and you can also fly fighters and bombers, drive tanks, jeeps, troop transports, and mobile artillery units, and captain battleships, destroyers, carriers, and submarines.
I played it for several hundred hours and then got tired of trying to find a server with some actual teamwork. My friend, who still plays all the time, tells me things have gotten better in that regard. If you do buy the game, make sure you download the newest patch, because it fixes a lot of bugs.
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<P ID="edit"><FONT SIZE=-1><EM>Edited by Twitch on 04/12/03 11:57 PM.</EM></FONT></P>