Mechwarrior/BattleTech is also a bunch of bad guys beating up on other bad guys.
Let's face it, most of the original TT games were designed in such a way that none of the factions were "the good guys" The reason for it was because if there were one or two that were "good guys" everyone would want to play that faction.
Now, I have not kept up with the lore since FASA pretty much folded in 2001, but while there were some good individuals in each of the houses, most of the leaders were out for the main chance for themselves.
I still prefer the "classic" game and even the technical readouts that expanded the game or changed it with the new clan tech, but I never got into AeroTech or the warships part of the game.
All that said, without a "good guy" or at least, resistance to the "bad guy" it's really hard to make movies. You need to have someone to root for, and someone to root against.
As for Warhammer 40k. I FULLY admit that pretty much every faction has blood on their hands. BUT, it could be argued....along with giving your debate opponent a large amount of potent drink beforehand so that you would win...that the Emperor is the "good guy" and that the loyal legions are trying to help humanity. (for the most part). Even to the point of sacrificing the psykers to keep the Emperor's will "alive" could be seen as a "necessary evil" to stay the powers of the gods of chaos.
Yes, some of the other factions can be argued the same way. It's even possible to say that the Orks are not bad...they just are following that nature of the genetics that were built into them.
It's very possible to create a movie or show where the human factions...or even the factions of Eldar, or Ork, could be portrayed as the "good guys" It's certainly possible for the Ultramarines or Frostwolves to be seen that way. All you have to do is compare them to Chaos Marines or Necrons and you can have a good movie.
All that said, I think 40k would be a better IP for movies/shows as you have flawed 'heroes" but you have much worse in the way of villains...depending on your point of view. This is preferred in modern moviemaking compared to the more simplistic plots of the 70s-2000.