If we have to stick to novels, and I'm going to be stuck on that island a while, I want something that can be read, reread, and re-read again.
5. The Brothers Karamazov, Fyodor Dostoevsky
* Every time I open this book up, I find a new head-game. Not necessarily good for a deserted islander's sanity, but hey, still great.
4. Paradise Lost, John Milton
* Not really a novel, but close enough to count, I hope. This would be for reading aloud to the birds and the dolphins and my girlfriend, Ms. Made-Entirely-of-Coconuts.
3. David Copperfield or The Pickwick Papers, Charles Dickens
* Because I don't want everything to be gloom and damnation and epicness.
2. The Adventures of Huckleberry Finn, Mark Twain
* Not only is it great, it stands re-reading well.
1. Robinson Crusoe, Daniel Defoe
* Sometimes, you want some escapist entertainment to distract you from your struggle for survival.
My favorite novel of all time is tough to pin down, but it's either David Copperfield, The Master and Margarita, or Terry Pratchett's Mort - the last being one that I wouldn't re-read, for fear of destroying the nostalgia value.