Some good changes are like
1. the open seamless neighbourhood, zooming into a household and zooming out to view the town
2. i like the city hall and the protests and other new buildings not seen before in Sims 2 like the Spa
3. going to ANY sim’s houses in town which you never can do in Sims 2 and visiting friends or stranger’s houses
4. the various TRAITS which determine the sim’s behaviour (ranging from insane to computer whiz to charismatic) and the distinguishable distinct behaviour that comes with those traits (e.g. the excitable trait whereby your Sim gets excited over little things)
5. your sim making friends and getting to know another sim character and one-by-one finding out all the traits of the acquaintance, the sim third party actually tells you what he/she thinks of you when your sim interacts with that sim character (for e.g. when i click the Get To Know interaction, the other sim character says “I think she is being very sociable” or “i think she is being creepy”
6. i also like the fact that i can go to the sim’s workplace (restaurant, office building, theatre) and school even though you can’t actually go INSIDE the building
7. i like the fact that you can choose what your sim does at work or in school (e.g. talk to co-workers, slack off, work hard, take it easy, work normally)
8. i like the new features such as picnic and being able to change the sim’s name in the city hall and that you can have triplets babies.
9. there is more flexibility and choice in controlling how your Sims look like (for example, morbidly fat to skeletal thin, different skin colours like red, green, blue which are not available in Sims 2)
10. I really liked the Story Progression and Aging options incorporated into the OPTIONS window in the SIMS 3 GAME. The Story Progression enables your Sim’s friends and neighbours to move to a different house, and get married and have kids and and hence you are not stuck with the same Sim characters and keep seeing the same Sim characters in your neighbourhood like in Sims 2. The Aging Option in Sims 3 prevents the sims from aging. In the Sims 2, there is no Story Progression but there is a cheat code in Sims 2 that prevents the aging of the sims and works just like the aging option in Sims 3.
11. i like the job, skills and special opportunities which make you go around town to do a task which can result in an improvement in relationship or job performance or another reward HOWEVER i wish there are more different opportunities available and opportunities made more frequently as it gets dull during the periods where there are no opportunities.