An entirely new 3-D engine makes the world of The Sims 2 more life-like and dynamic. The Sims 2 will also introduce an all-new "Create-A-Sim" feature. This allows you to customize the facial features of your Sim with a few simple clicks, to a level of detail never realized before. In The Sims 2, players are now able to build dwellings over two stories and have the ability to coordinate and customize the homes of their Sims to a new degree of design with all-new furniture, lighting and objects.
I never played the first one... This one has a better premise I would say though.