Medium speed turn-based strategy games, the ultimate 1 vs 1 challenge.
Kingdom management including researching techs, buildings, learning and deploying different troops, and an overall focus on strategy.
With only two players, there is noone else to blame for defeat.
Games are turn-based but have a much longer time limit.
(Most games are medium speed Player-Ends-Turn style, similar to "hotseat" TBS games)