When I had them they were Sylvanians. Love them!
I am not personally a fan but I strongly prefer natural toys and I avoid products for children made in China. They use a lot of plastic in the accessories. The animals are cute-ish but the other stuff is not. They are certainly less annoying than a lot of toys aimed at similar aged kids.
I think the age suggestions on them are much too young. MIL got some for little sister when she was three, and was much too young. Now, at almost 5, they are getting some play. there as still some accessories I'd be crazy to give her.
We have some animal sets and the kitchen set. She's got different houses, but not the calico critters house.
In general, I like them, and they fill in the doll box collection fine. I don't think they are worthy of extensive collecting, unless a child were very taken with them.