Vorkosigan series: I started with the prequels.
Falling Free is a good book
Shards of Honor is enjoyable too
Barrayar - gave up after 1/3
The Warrior's Apprentice - gave up after 1/2
These books are more suitable for teenagers in my opinion. After the first half of the Warrior's Apprentice I decided that this is not for me. Way too naive and straightforward. Then I read more of the story on Wikipedia. Wow. I am glad I gave up on the series. Yeah, he gets into trouble easily but gets out of it equally easy.
Caution, spoilers here:
http://en.wikipedia.org/wiki/Vorkosigan_Saga
I will not quote, go to the above link and read a few contents.
But back to topic.
Dune is a classic without doubt. I would be still curious the hear more about the other books. Having disliked Dune Messiah, I am a bit skeptical towards them.
What I like in sci-fi is alien races, secrets, mysteries, discovery with REALISM. Something that is imaginative and also believable. Political intrigue and cartoon/hollywood style superheroes turn me off. We have enough of the former in real life (and that is sometimes fascinating), and enough of the latter in Hollywood movies. Books should be about something else.
Dune is a great book, because there are many insights that go beyond the story. Paul may be a hero, but he is not some instant super-kid. It is also realistic in its own way that is consistent with the world. Compared to the world of Dune, the world of Miles Vorkosigan is dull and unimaginative. The quaddies in the prequel Falling Free were a nice novelty and that kept me going. For a while.
I really do not understand how Barrayar is in the same category as Dune (as both are Hugo winners).