General greetings (Formal)
How are you doing?
How do you do?
How is everything?
General greetings (Informal)
What’s up?
It's Good to see you.
How’s it going?
How are things with you?
Greeting a person you haven’t seen for a long time (Formal)
It has been a long time.
It’s been too long.
What have you been up to all these years?
It’s always a pleasure to see you.
I’m so happy to see you again.
Greeting a person you haven’t seen for a long time (Informal)
How come I never see you?
It’s been such a long time.
Where have you been hiding?
Long time to see.
It's been ages.