I think the look of the first game was better. I feel like they totally ruined the style of starcraft by making it all cartoony. I loved the darkish "realistic" metallic style from the first game. Everything now looks like a fucking cartoon.
One thing I think they did right with this game is the balancing. In starcraft 1 there was probably only 2 types of strategies for each main race. In starcraft 2 you have way more options on how you want to carry out your attack. The only problem I see is theres yet to be any real end game fighting so far in 99% of my matches. I don't even think ive seen a battleship or a carrier used yet because battles never go longer than 15-20mins.