Looking for something for running battles from say 13th through 15th centuries. Wars of the Roses, 100 yr war, Scottish independence wars, etc.
Horse 'dominated' the battlefield on and off - alternating with foot - from ancient antiquity (~3000 BCE) until WW1, so not really a persuasive argument, I'm afraid. The effect of a charge was always more morale than physical - unless morale was broken. From ~1080 to around 1380 mounted knights were considered the main arm of battle, but that was as much to do with aristocratic pride and poor quality solid infantry as anything - and that only applied in western europe in any case.Archers are too damn powerful, and cavalry doesn't have the punch that it really should in the age of impact warfare, but it plays well and to be perfectly honest I'm not sure there are many games out there that properly simulate just how devastating a charge of armoured horsemen was. I mean there was a reason they dominated the battlefield for 400+ years.
Also, Ganesha Games do a rather nice set of fantasy rules - Songs of Blades and Heroes - that would be eminently usable for medieval wargames with armies that aren't too large.