In civ3 (vanilla, I don't know anything about other versions) there are only Deserts, Flood Plains, Tundra, Hills, Plains, Grasslad, Forest, Mountains, Snow-Capped Mountains, Jungle, Pine Forest and Bonus Grassland. I'm not talking about ocean, sea and coast. This means 13 types of terrain.
Will these be the only ones in Civ4? I think they should be at least 25 types of terrain:
Tropical wet forests
Tropical dry forests
Savanas
Rain Forests
Temperate evergreen forests
Jungles
Pine Forests
Palm-Trees
Stepes
Sand desert
Rocky desert (I'm not sure this is the english name, but I hope you understand)
Plains
Arid Plains
High-Altitude Plains
Grassland
Bous Grassland
Hills
Forest Hills
Mountains
Forest mountains
High mountains
Tundra
Frozen plains
And near rivers or lakes not only Flood Plains, but also Fertile plains.