Some are grateful for the opportunity and some say - I had to work hard on my success and I see no reason to be grateful - individual thing really.
true but they forget that if not the "opportunity" this country gave/gives them, they wouldn't get a chance to say that "I had to work hard on my success and I don't see no reason to be grateful" and make it as far as they did here. Yes, I believe they have a reason to be grateful after all.