just found this thread, so I thought I'd throw my $.02 in as well. some of my favorites have been mentioned already, so I will try to omit those.

The Stand by Stephen King
truly an epic read that takes the reader through several levels of reality before you reach the final layer of truth. not for the casual reader, but absolutely worth the journey.

Battlefield Earth by L. Ron Hubbard
yes, that L. Ron Hubbard. possibly the most comprehensive plot development I've read in any genre. I would compare the scope of this book to the lies of The Count of Monte Cristo or Great Expectations without blinking an eye. the story takes you from the smallest seed of an idea and follows it all the way through to where hat seed has become a mighty mature oak. also not for the casual reader; however, truly worth the investment. and really, how can you not read a work of science fiction by the man who brought us Scientology? seriously, the man invented a religion! no offense intended. the only thing this book has in common with the movie "based" on it is the title, and is the entire reason that John Travolta is dead to me.

The Dresden Files by Jim Butcher
best. series. ever. hands down. this man is a gamer, fantasy and sic-fi geek that writes for gamer fantasy sic-fi geeks. the character development is excellent, and the plots and nuances to the stories tie together so perfectly to paint a picture of a world so like our own, yet so much deeper and inviting. the modern noir aspect to the narrative is spectacular without overshadowing the story. Butcher has taken the Wizard Private Investigator in Modern Day Chicago sub-genre and breathed new life into it! Okay, okay....so that genre may in actuality be wholly comprised by the Dresden Files series alone, but who can resist a talking skull, holy knights, fallen angels, three different kinds of vampires, one kick ass blonde police lieutenant and, dare I say it, an undead tyranosaurus rex? and that's just in the first three or four books! seriously. read it! the Sci-Fi Channel series loosely based on this series, while okay, really dumbed down the essence of what JB put into the world he created...kind of like how Sci-Fi has ruined pretty much every series they've gotten their meat hooks into. KC, you have been warned!

Codex Alera Series by Jim Butcher
Jim Butcher does high fantasy. amazing character development and exceptional storytelling. the world of Alara is unique and elaborate, full of magic and intrigue. the plot this series covers is, again, immense and covers ground from political espionage to epic pitched battles to the life story of a young man as he learns to cope in a world to which he was born an outsider. I personally guarantee you will not be disappointed by this series. in fact, if you read the entire series based on my recommendation and can truthfully claim you hated it, I will buy you a paperback of your own choosing as compensation for your lack of a soul.