NPR's List of 100 Greatest Fantasy/SF Novels of All-Time
This is a pretty great list. Over 60,000 people voted on the titles, so the list reflects popularity.I've read a bunch of them but certainly not all of them. You'll note there are no children's or YA novels on the list: No Narnia, no Harry Potter, no Golden Compass, no Eragon, etc. Ender's Game, interestingly, was allowed in and ended up at #3. Obviously there's not a clear dividing line between YA and Adult. There are a lot of classics on the list, and there is a lot of stuff on the list not suitable for kids. However, if you're a genre fan and looking for something to read, you will find a lot of great ideas on this list.