Use the phrase "It's great to ___" in social situations to say that something makes you happy:

It's great to see you.

It's great to finally meet you!

More specifically, you can use the phrase "It's great to have you ___" to talk about someone's current situation:

It's great to have you back.

It's great to have you as part of the family now.

It's great to have you with us.