Ghengis John said:
Well it would be bad enough if it was just the Terran forces.
http://en.wikipedia.org/wiki/Tyranids
http://wh40k.lexicanum.com/mediawiki/images/4/40/Tyranid_Trygon.jpg
http://en.wikipedia.org/wiki/Eldar_%28Warhammer_40,000%29
But I agree. Which is why i said if games workshop couldn't sue, nor can Blizz.
The insectoid alien isn't exactly unique, starship troopers film (& I assume descriptions from the book), aliens etc
Technologically advanced aliens are pretty much a staple, although I do remember once seeing a design with a Protoss helmet and I was totally 'shit, that does look like an eldar helmet' and the Eldar are very original design visually.
The addition of a large brutal warlike race could be orks...or klingons, or loxans or chewbaccans (whatever they are called).
But yeah, I agree, there are enough stylistic and other similarities to say that starcraft was certainly inspired by 40K on many levels.