Interesting how many people on the forums have been exposed as pirates lately.
(Not implicating anyone in this thread, just saying.)
Well I only played through Cape Town, but I can see where the main improvement is in this edition of Asphalt already: the take downs. They look better (not as good as Burnout: Legends, but much better than Asphalt 5) and are a lot easier and more fun to pull off. And honestly, with 40% (I think?) of the racing being entirely focused on take downs it makes all the difference.
Some other smalls tweaks have been made, for better (slightly improved graphics) or worse (no mini-map), mostly for the better...but the takedown events are fun...damn fun...and the multi-player is relatively well-realized. The "adrenaline" mode is pretty cool, especially (again) in the takedown modes, where you feel like you're tracking opponents, diving at them like a missile.
This could not be any more different from Real Racing 2 and still be a racing game...which is a good thing, because having each on my device means I get the best of both worlds.