There's a few topics here comparing the various Sims versions, but I didn't see one comparing Sims 2 with its predecessor.
I played Sims 1 back in 2000 and loved it. It was constantly producing funny moments and it was probably the first game to really produce genuinely moving moments too. I remember being distraught when my first family's daughter got taken off to military school.
I recently started playing Sims 2 after my brother's old room was cleared out and I came across the CD. I like it, but I'm not sure yet that it beats the original.
A few pluses and minuses.
Plus - It's basically the same game with better graphics. They didn't mess with the basic formula that made it a great game.
Minus - They did remove a few funny things that always made me chuckle - Parents no longer boo their children while they practice the piano, Sims no longer open conversations with "Wet lemon!".
Plus - The community lots and travelling round the neighbourhood are great additions.
Minus - Obviously the Sims is made by a US company and models US life, but that wasn't an issue in the first game. The Sims 2 is even more US-centric though, and is littered with phrases that mean nothing to me (eg. "Gussy up"). The house and clothing styles don't really include anything that looks like it could be from outside north America.
Minus - Sims 1 had a number of game-breaking bugs in the initial release, but these were quickly patched. Sims 2 seems to be quite buggy and fragile even after patching.
Minus - A number of annoying issues from Sims 1 are still present in Sims 2.
- Sims still cancel a task to complain that they want to do that task. (eg. most commonly: you tell a sim to go to bed and they cancel the task to tell you how tired they are!)
- Sims autonomously make dinner rather than serve dinner and there's no way to convert them to serve, or put the food away if you cancel it.
- Some tasks still take ridiculously long: greeting people, collecting plates, stopping reading/studying.
Plus - The phone options are much better.
Plus - The aspirations system is a good addition.
Minus - Custom content in Sims 1 just worked. In Sims 2, about 50% of stuff I've tried either doesn't appear in game at all, or appears in the menus but cannot be placed. I assume this is because of dependencies (I only have the base game at the moment) but there doesn't seem to be any way to find out what those dependencies are.