This is an interesting question inasmuch as it depends on other factors - one - it would be all right if you could retain your health and strength throughout, including mental strength, two - if you could somehow be independent of other people and three if there was enough interesting going on in your own life to keep you occupied. There are other smaller factors but I think this covers the main considerations. Having said that I would certainly like to see an end to wars, a cure for cancer and many other ills including heart disease and diabetes. Inventions? I would like to see a substitute for petrol and diesel - I remember reading something ages ago about sea water (well there's plenty of that) but it may have been a fantasy. It would also be interesting to see space travel if it is indeed possible. All these things look like insurmountable mountains, but other equally as difficult have been conquered before so maybe it is possible. "Man is an animal with his feet in the gutter and his face raised to the sky." or something like that.