I'd probably say something like this:
"Johnny, it's a real honor for me to meet you. It's been my biggest dream since I was a kid and now you actually stand there in front of me. Even a thousand words wouldn't be enough to tell how much you mean to me and how much I love you. If someone can be perfect, it's you. I've always been so crazy about you and I think I'll always be. I wish nothing but the best for you and your whole family."
That's what I've been planning to say if I'll meet him some day. But I don't know if i'd be even able to say anything in the real situation.:)
Assuming I don't die of shock (haha), I would probably say something like this.
"Johnny, I just want to say thank you. Thank you for your movies and wonderful characters. I love them all! You're such an amazing and talented actor! And I admire how kind and humble you are even though you are such a big movie star. And you're so beautiful! WOW!! I've never seen a more beautiful man in my life!! Most of all, thank you for being such a hero and inspiration for me. I don't know what my life would be like without you in it. You give me so much happiness and joy. Thank you so much. I love you, Johnny"
Then I would give him a HUUUUUGE hug and maybe a kiss if I'm lucky :D
I would say,
"Hey Johnny, we all know you're sexy, probably had it said to you millions of times..I would just like to say thank you for the joy and entertainment you provide for many around the world, and for being a humble realist. You inspire unknowingly, and are an experienced soul.
Then I would continue on to ravish him and eat his face off.