I'd say Dark Heresy is rather setting heavy, so I dunno how easily you could transfer it to others.
That said, it has, bar none, the best critical tables in the history of the world.
Better than Rolemaster? Because unless it has electrical criticals that can fry your nervous system killing you instantly and 'providing a fine light show' I have to disagree.

Or the classic moving fumble "You trip over unseen, imaginary, deceased turtle. You are very confused."
The Warhammer 40k Universe is very much it's own place. It's an oppressive dark gothic universe where the bad guys are horrific alien mostrosities like the Genestealers or literal Demon-Gods of chaos seeking to twist all reality to thier own image. It's a world where the
good guys don't hesitate to incinerate cities, or even whole planets, to get their prey. It's a world of fanatics, genetically engineered super soldiers, tech-cultists praying to machines they no longer understand, half-sane Espers sifting the minds of the inhabitants of giant hive-cities and normal men simply trying to get by in a hostile universe.
If that's not what you are looking for then seperating the system from the world will be more work than it's worth, they are tightly integrated.
Mind you it's a big universe, with 10s of thousands of inhabited worlds, fleets, space stations, alien species, etc. You can find a place to tell most any story you want, but it will always have chaos lurking in the background and fleets of murderous fanatics waiting to strike down heretics even if your PCs are currently vacationing on a paradise planet.
If you want a generic system and prefer normal human level PCs I'd suggest GURPs I think you can dl a quickstart rules set from the SJ games website if you want a look at it. However I find the GURPS system kinda breaksdown at higher power levels. If you're going to want a higher power level like cyber-soldiers, super powered aliens and mech combat I'd go with the Hero system or an older SF system like Mekton.
BTW GURPs is usually considered to have the finest supplements in gaming and several of them are for SF settings from Krishna to Transhuman space.