I'm reading some strange comments. Of course, cavalry should be faster; that's the principle of the unit. It already has minor penalties, such as reduced capture attack and suffering damage multiplication. The solution isn't to have a common citizen unit with a lance destroy a very expensive champion unit! The champion cavalryman is one of the most expensive units, so it must be one of the strongest units.
Furthermore, I believe it's necessary to balance champion units between each civilization. If I'm not mistaken, the Persian and Selucid champion cavalrymen are better suited to long melee combat than other civilizations because they have better range and armor. Their range needs to be nerfed and made sure they can't stack too much in a small space. For example, champion chariots already have this feature. This will allow the infantry to do their job.
Additionally, it is absolutely necessary to remove the 20% extra life tech on champions.