Oops sorry, I would say that I was a fan of their music!

If it was like just on the street and I don't want to freak them out so...
"Oh, Hey! You're SHINee right? I have a friend that really likes you! I quite like your music too"

And theen, hopefully they'll find me interesting and talk to me and then I can get close to them... lol fantasies that will never happen. But they'll never know that "friend" I was talking about, was me kekeke <3
However if it was at a concert or fansign I'd probably just say, "SHINee I love you!" Hehe <3

OMFG I LOOOOOVE U. JONG CAN I TOUCH UR ABS. KEY CAN I TOUCH UR . TAEMIN CAN I KISS UR FACE. ONEW CAN I PINCH UR CHEEKS. MINHO LET ME HUG U

I LOVE YOU SO MUCH, CAN I PLEASE DANCE WITH KEY AND TAEMIN, EAT CHICKEN WITH ONEW, WAND WATCH MINHO AND JONGHYUN SHOWER ERHM I mean jog with them :D

Thank them for being who they are, and that they helped me find the real me and become a better person.

I will scream first and my first word for them would be saranghae shinee

thanks for being my shining inspiration you'll always have my support oppas ^.^

If I manage to say something( while fangirling like crazy), I guess I would say:

"SHINee Saranghae!!" <3 or
"OMG you are Key!!*points at him+fangirling even more*" (he's my bias xD <3)

you are my everything

I would thank them for making my life so bright and colourful, I guess...