This is a hard one! I am young, in my 20s and I really enjoy my life, as every young person should do. I can't and don't want to trade it with some rich or famous person, it would be not worthing at least for me. Don't need it.
I guess I would trade my place with an old man who knows that its time has gone and is about to leave this material place. Who passed through life already and I would love to see what's in his head looking at the new generations. I would make treasure from all his thinkings, the moments he regretted and chances he maybe never took. It would finally make me understand that our time is limited and we have to live it fully. That I am still able to do things that from his perspective are now impossible and he would probably give everything to have the chance to go back and be where I am.
Surely I would appreciate every moment way more than I am actually doing.