There is a different gridsize in operation in SimCity 4 and in The Sims 2.
To demonstrate the difference, I made a city with a simple grid in SC4.
Moved it into Sims 2 to try the different sizes of Lots.
These are the sizes we have available.
The tiniest Lot (2x3) fits into2/3 of a SC4 1x1 tile. With room for some decor.
Two of the tiny Lots fit back-to-back into a 2x1 SC4 tile. With room for some decor.
Here are SC4 blocks 1x2, 1x3, and 2x3.
For larger lots, most of them do not fit exactly. Here's a screenshot of the only three that do. There's a 3x3 Lot, a 3x5, and a 5x5.
So if you want a Sims 2 city with houses exactly surrounded by roads, you need to make it with a SimCity 4 grid of 1x1 and 1x2 and 2x2, and then use these house sizes.
The large image above shows how the SimCity layout constrains the Sims 2 layout.