The 49-year-old actor has filmed a video blog in which he confesses he has a huge crush on The Amazing Spider Man actress—who is 27 years younger than him.
In the comic video posted on his official website, he says: "Emma, I think you're all the way beautiful. Not just pretty, but smart and kind-hearted. And if I were a lot younger, I would marry you. We would have chubby little freckle-faced kids.
"We'd laugh all day long, go camping and play Yahtzee. Tell ghost stories by the fire."
Jim—who split from former Playboy model Jenny McCarthy after five years together in April 2010—acknowledged the age gap in the video, and jokingly admitted a relationship between the pair would be inappropriate.
He added: "And every day, for the rest of your life, you would thank God that I was the appropriate age for you. But I'm not. I'm 49.
"I have lines on my face, sometimes a little gray in my beard, and it takes me a little bit longer to pee than it used to."
He signs off the video by wishing Emma—who is rumored to be dating her Spider Man co-star Andrew Garfield—the best with her career.
He said: "Anyway, I just wanted to let you know how I felt. I think you're very special and I wish you continued success and artistic fulfilment. But most of all, I wish you love and contentment."