I'm twenty hours into Odyssey. It's good, and if I'd played it before origins I'd be blown away, but as it is I prefer origins.
Otherwise its a carbon copy, take out the pyramids and Egyptian mythology, replace with greek but more emphasis on sea battles, but that's about it.
I'm yet to fight any mythical creatures yet though, so maybe that will change it.
Try 302 hours and still no where near finished.