Did you play WarCraft III at all? its pretty much just a hyped up 3D engine from that. Blizzard did not want ture realistic graphics for this game. They made this known long ago. They made the game how they wanted. Yes i did not care for the graphics when i first started playing, now though, i wouldnt have it any other way. Dont be fooled by screenshots, if you ever get a chance, play the game, the graphics look MUCH better while you are playing, not looking at screenshots.
Considering how many other games are going for "Realism" in thier graphics, this is an odd concept for Blizzard to do, but, it works. And it works well. Its a nice change of pace if you give it a chance.