dont u think the unit provided in civ 4 are very less. i mean after doing so much research u should get around a dozen of units with different persona and power but u get is a 5-6 units in a given era.

Im fairly sure that the units that you can get are equal if not greater than in previous versions of the game, and to be honest, you really only need around 3-4 different types in any given era:
such as One Type of Defender, One Type of Attacker, One Type of Transport (for transporting across continents). Overall, I personally only keep the most strongest of the lot, hell I sell my warriors as soon as I get them since they're nothign compared to say the swordsman.

If you get the expansions (Warlords and BtS) they add more Civs, Units, Leaders, Mods and Scenerios