My DD did not play with other kids really at all till about mid-4. Now she is very social and would have a playdate every day if she could. My son is 3 and has been playing beautifully with other kids since 2, but he's been fortunate to attend a small daycare with some slightly older kids who are also bright and verbal. He's also very socially skilled--much more so than his sister was at this age.
DD was not in a good daycare environment for her and seemed to just decide that the other kids were not fun, preferring teachers instead. In a large group she sometimes still gravitates to the teacher; she prefers one on one. I think a lot can depend on finding the right other kids.
