SAY OR TELL

Usually if you are going to use quotes for direct speech we would probably use:
said, "quote." over told him, "quote"

if you get rid of the direct quote and just make it reported speech, then it would be good either way, but I think told him sounds better.

A couple other things are a bit awkward but taken out of context it's hard to say.
I saw another person sounds like you just met him or you don't know him
and told him I didn't think I had ever met a more interesting person. - strange that you find him the most interesting after having just met him. Or it may be 2 different people? Or there was a time lapse not mentioned?

Anyway, I hope that helps with the original question.

nunzia wrote:What is the correct use for this sentence?

I saw another person and told him 'I did not think I had ever met a more interesting person.'

OR

I saw another person and said to him 'I did not think I had ever met a more interesting person.'

THANKS.

For me the words that seem questionable are -saw- and even -person-
If you are speaking to a person you would have met them, not be seeing them, if that makes sense to you.
Also, you know he is a man, so it would be more specific to describe him as a man, and not a person.

eg, I met a man and said to him, 'I don't think I have ever met a more interesting person.'

I also think the tense could be changed. Correct me if this is wrong.