Completely new dex filled with 156 Pokemon, that are the only ones you can recreating the feel of the originals, of only having 151 monsters, but doesn't make it so you unable to use any old Pokemon like FRLG, by allowing you to trade any of them over if you have two DS and two cartridges of BW/B2W2, in my case on 3DS and DS W and W2. Good Maps that are fun to explore though like Pinwheel Forest, or Village Bridge.
It's not as handholding as people make it out to be, like the first gym, I didn't even know I could get the elemental monkey their and I was still able win.
Only real problems I have would be that it's more linear, but that is due to the story, so that's really depends on how you feel about it.
And some Pokemon Designs are really hit or miss, I find some of the hit to really hit hard but I can understand not liking all the new monsters introduced.

But some Really good one's I will list here:
Gigalith
Scolipede
Krookodile
Maractus
Sigilyph
Reuniclus
Vanilluxe
Escavalier
Jellicent
Galvantula
Eelektross
Chandelure
Haxorus
Shelmet
Stunfisk
Golurk
Bouffalant
Braviary
Hydreigon
Volcarona

and some of the more note worthy bad ones:
マッギョ
Cryogonal
Klink
バイバニラ
Garbodor
Basculin
Swoobat
The monkeys