Is Civilization IV as good as Medieval 2 Total War

This is a matter of personal preference. Medieval Total War is a combination of a turn-based game alongside Real-Time Strategy. You can literally command your armies and decide battles in real-time whereas in Civilization IV, you cannot.
On the other hand, Civilization IV is more of a strategic game in itself. The visual effects or models are not quite as detailed (a little more animated) than Medieval, but it is acceptable for a modern-day game.

Civilization is a great game. Go get the newest version beyond the sword.