I can admit that the pikes are very easy to come by. Knights are two (if I remember correctly) techs away and takes forever and you (at least I) starts to miss the techs that you could have had. But sure, if you really wants to.
Can't say that I have gone for the knights straight a head in any game or seen an AI done so either (they seems to like the melee line and Longswordsmen). Although I have gone for the Pikemen and some AI also seems to like them.
Pikes really should come after Knights historically. Knight dominated the battlefield in Europe from about 1100 to the Battle of the Golden Spurs in 1302, when a large number of French knights were defeated by a bunch of Flemish peasants wielding pikes.