1. No, it's nothing like fable. Fable turned in to more of an Action Adventure while Skyrim is a full-fledged RPG
2.It's massive. It might not be the largest in terms of sheer size of any game that I've played. In terms of actual content (eg. quests, dungeons etc.)it's second to none. Without question.
3. Some issues such as clunky menues (the perks menu and the favourites system) for consoles, texture problems and a crappy map keep it from being a perfect game. That being said, overall it lives up to the hype of being one crazy big open world RPG that's always loads of fun and never feels like a grind to get through.
4. The graphics are good. A huge step up. They aren't amazing however. Things are best viewed from a distance or flaws become rather evident (eg. look at a tree up close to see that it's a blocky mass of polygons).
5. Skyrim. Hands down. And I loved RDR