Too be fair... I think... the Marines did die rather easily, though. Taking only a sword stab and a single shot at times. It seems their bodies/armor got severely under played. *shrugs* I'm no expert, but the lore does imply they can and should be able to survive far more than single shots or stab wounds and keep on smashing face.
Personally, I find the Space Marines rather boring, though. Its one thing to be badass, but the Space Marines are a blatant ego-boost common in gaming. Its tripe, if you ask me. Superhuman's who can literally crush all in their path... boring and so unrealistic. The Sisters may be fanatical crazies, but at least they win through sheer will, belief, and awesome. Not because they are genetically-engineered-cheese incarnate.
GW has always been notorious for 'hyping' every figure in every army list. I know they want to sell figs, but... not -everything- can be devastating, terrifying, ass-kicking, name-taking, faster than lightning with unerring accuracy and the toughness of a mountain. There's nothing more fun than to read a 'sales pitch' for some Eldar Guardians, getting them on the table... and then watching them disappear to a stiff wind. :)
If we put fluff against fluff, no one would ever lose! :) I learned long ago that you can't rely on fluff most of the time when it comes to game-mechanics anyway, especially when you're limited to a single d6 mechanic. There's only so much range in there.
Glyphstone touches on the vein of history that I think is relevant: Marines were made to battle Mankind's most dangerous enemies. That doesn't necessarily mean they're 'better' than all of those foes, but they should definitely be mankind's 'best', I think. But I am on the same bus as you, Xanatos - I've always found the Marine literature pretty boring/bland. The ultra-religious gung-ho vibe is just so very 'meh' to me. I know the majority of GW's customers eat it up, though, and I definitely don't mind being in the Xenos Minority!
Xenos - we are 'people' too!