You're getting:

-3 neighborhoods that were made by the creators, plus some families in each neighborhood. Plus the ability to custom make your own.

-Serious stuff regarding how your sims look. It used to be just outfit change and the hairstyle came with the head, but now, you can change skin tone, eye color, hair color, hair style, body type, clothing for every category (formal, every day, pj's, undies, swimming, etc) instead of just one outfit for every day and the game's choice of night clothes and formal wear like in the original Sims.

-The ability to have kids that actually look like your parent sims rather than two blond parents with a dark-haired kid like in the original Sims.

-Needs and wants for your sims instead of just needs.

-TONS more detail in EVERYTHING! You can actually watch your sim cook, and you see "Milk" on the milk carton and EVERYTHING!

-More stuff that is just so EPIC that I can't think of it all just now ;-;