I like the first two, and the chess one's pretty interesting though I can't imagine I'd have an easy time getting someone to stand still long enough to hear the whole thing as an argument. But I don't really like the last one. You've been tricked into accepting his premise, that death lets you create more meaningful art, and trying to regain ground from there. It's that premise itself that you should be arguing against--point out all the great literature and art that isn't about death, and that you could still have all of that once death was gone. Also point out that to someone with cancer today the availability of art is probably less valuable than the availability of a cure would be, and there's no reason to assume that'll change if you double his age, even if you double it several times.