This is not a hard question to answer for me.
N. He is one of the most tragic characters Pokemon has ever seen (he was the most before Sun/Moon came along), and the things he says are some of the most inspirational lines of dialogue to appear in a video game, especially the quote at the end of White when he's about to leave:
You said you have a dream... that dream... make it come true! Wonderful dreams and ideals give you the power to change the world! If anyone can, its you!"
That quote made me cry first time reading it, because I had been going through a few self-esteem issues at the time of playing.
Back to why I love him, though. One thing I spotted was that in B2W2, when you go do the season battles with him in post-game, he properly identifies as a Pokemon trainer. This moment, as well as that moment just before Victory Road where he talk to you, is when I realised how his character had developed so much. He accepted being a Pokemon trainer, instead of shunning the term.