Look, we all know SCII has fantastic graphics so I'll skim over it.
The animations are smooth as silk, the lighting and spell effects are
awesome. The little details present in animations on unit death, such as a zerg
unit's skin coming off revealing the skeleton underneath, or a Hellion blowing
up and seeing a tyre fall off it and fall of the side of a cliff, etc. Bottom
line is: It's a beautiful game.
Now for some gameplay changes. it seems Starcraft II has borrowed many
functions from Warcraft III such as rallying to t so you can move in a specific
path without having to babysit units.
You can also multi-select the same type of buildings and build multiple units
simultaneously. This reduces the macro required for managing unit training.
Unit AI is vastly improved from the first game. No longer do you have to
control medivacs (similar to medics from SC1) seperately. If you attack-move
with medivacs they sit with your units in a battle instead of moving ahead.
Pathing improved, general AI improvements, etc.
Although these seem like simplifications of gameplay mechanics it also brings
a new depth to gameplay. SC1 veterans will have no problem transferring their
skills over to SC2 with a little bit of getting used to. New players will find
it easier to get into thanks to these features.
Overall, this is the best RTS I've ever played. Not overly big (Supreme
Commander) and not too simplified (Dawn of War II).
gl hf!