hm, you can try something like this:
SELECT g.GameName FROM members m, games g
WHERE m.Username = '$Username'
AND m.Password = '$Password'
AND m.Game1 = g.GameID
AND m.Game2 = g.GameID
AND m.Game3 = g.GameID
AND m.Game4 = g.GameID
AND m.Game5 = g.GameID