Yeah, Norse, repeating what you said wont bring the discussion any further.
If the terrain is moderatly flat, with no obstacles what so ever, if the infantry have run out of ammunition, if they have no coherent teamwork whatsoever, and if the infantry players have no experience, then yes, 4 lancers can probably kill them all. However, give me 3 skilled bayonet-meleers and I can probably achieve the same thing in the same situation.
If, however, there is obstacles (Trees, rocks etc), if the infantry have ammo left, and if the infantry have even the smallest amount of coherent teamwork, and if they have even the slightest experience, you wont manage to kill 15 of them. Lancers are so easy to counter, it is insane.
The "problem" is that people face lancers the way they face other melee threats - bayonets. Using a bayonet agaisnt a lancer is, in most instances, as stupid as using a butterknife against a heavy cavalry Sabre. The lancer has the melee-range, the speed and the maneuverability. Dont try to match him in any of those areas, and you'll be fine.