Depends on the game.
Red/Blue/Yellow
Welcome to our Pokémon Center!
We heal your Pokémon back to perfect health!
Shall we heal your Pokémon?
...
Ok. We'll need your Pokémon.
...
Thank you! Your Pokémon are fighting fit!
We hope to see you again!
Gold/Silver
If it's morning:
Good morning!
If it's day:
Hello!
If it's night:
Good evening! You're out late.
The rest is as follows:
Welcome to our Pokémon Center.
We can heal your Pokémon to perfect health.
Shall we heal your Pokémon?
...
Ok, may I see your Pokémon?
...
Thank you for waiting.
Your Pokémon are fully healed.
We hope to see you again.
Ruby, Sapphire, and Emerald
Hello, and welcome to the Pokémon Center.
We restore your tired Pokémon to full health.
Would you like to rest your Pokémon?
...
Okay, I'll take your Pokémon for a few seconds.
...
Thank you for waiting.
We've restored your Pokémon to full health.
We hope to see you again!
Diamond/Pearl/Platinum
If it's morning:
Good morning! Welcome to the Pokémon Center.
If it's day or night:
Hello, and welcome to the Pokémon Center.
The rest is as follows:
We restore your tired Pokémon to full health.
Would you like to rest your Pokémon?
...
OK, I'll take your Pokémon for a few seconds.
...
Thank you for waiting.
We've restored your Pokémon to full health.
We hope to see you again!
Soulsilver/Heartgold
Before obtaining 4 Trainer stars:
Hello, and welcome to the Pokémon Center.
We restore your tired Pokémon to full health.
Would you like to rest your Pokémon?
...
OK, I'll take your Pokémon for a few seconds.
...
Thank you for waiting.
We've restored your Pokémon to full health.
Please, come back again any time!
After obtaining 4 Trainer stars:
Introduction (First time)
Hello, and welcome to the Pokémon Center.
We restore your tired Pokémon to full health.
Would you like to...
Th-that Trainer Card!
That wonderful shade! And all those stars!
I've seen several Trainers with Violet Trainer Cards up to now...
But you're the first to top them with that impressive Trainer Card.
Please, , may I please heal your Pokémon?
...
Introduction (Second and subsequent times):
Great to see you, !
You want the usual right?
...
Post-introduction:
I will be pleased to take your Pokémon for a few seconds.
...
Thank you for waiting.
We hope to see you again!
Black/White And 2
If it's morning:
Good morning! Welcome to the Pokémon Center.
We restore your tired Pokémon to full health.
Would you like to rest your Pokémon?
If it's day or night:
Hello, and welcome to the Pokémon Center.
We restore your tired Pokémon to full health.
Would you like to rest your Pokémon?
After obtaining a Gold trainer card:
Introduction (First Time)
Would you like to...
!
Th-that Trainer Card!
That wonderful shade! That sparkle!
I've seen several Trainers with Silver Trainer Cards already...
But you're the first to top them all with that impressive Trainer Card.
Oh, , may I please heal your Pokemon?
Introduction (second and subsequent)
Great to see you, !
You want the usual, right?
And Finally X/Y
If it's evening or night:
Good evening! Welcome to the Pokémon Center. Would you like to rest your Pokémon?
Yes:
OK. I'll take your Pokémon for a few seconds, then.
Thank you for waiting.
We've restored your Pokémon to full health.
We hope to see you again!
No:
We hope to see you again!
If it's the player's birthday:
Upon entering Pokémon Center:
Happy birthday to you, !
Many happy returns, ! I hope this will be a wonderful year for you!
If player talks to the Nurse:
Happy birthday!
Please keep visiting the Pokémon Center for many years to come!
Now, would you like to rest your Pokémon?
Yes:
OK. I'll take your Pokémon for a few seconds, then.
Thank you for waiting.
We've restored your Pokémon to full health.
We hope to see you again!
No:
We hope to see you again!
If encountered in the Battle Maison
If player talks to the Nurse:
Huh? Do you want me to restore your Pokémon's health?
...Listen. As you can see, I'm taking a day off today.
Once I leave the Pokémon Center, I'm an ordinary girl, OK?
I'm quite stressed out from work. Today, I'm letting the stress out by watching battles.
When I go back to work, I'll do my job, so please leave me alone today, OK?
After obtaining a Gold Trainer Card:
First time:
Hello, and welcome to the Pokémon Center.
Here we restore your tired Pokémon to full health.
Would you like to...
Th-that Trainer Card!
That wonderful shade! That sparkle!
I've seen several Trainers with Silver Trainer Cards already...
But you're the first to top them with that impressive Trainer Card.
Oh, , may I please heal your Pokémon?
Source:This-->http://bulbapedia.bulbagarden.net/wiki/Pokémon_Center_Nurse
All credit goes to Bulbapedia
