It’s the age-old conundrum: Do you play a bad game for an amazing setting? The list of great games with bad systems is too long to list in its entirety here, but we’ve all seen such games, and I’m sure can list at least a few off the top of our heads and mostly agree upon them.
MechWarrior? Chill? Rifts? Shadowrun? Marvel Super Heroes (the TSR yellow-box edition)? Earthdawn?
Obviously, I’m sure there will be people who insist that the grid systems in “Chill” and MSH were quite innovative for their time, or that people just don’t understand the complex nuances behind “MechWarrior”, “Shadowrun”, and “Earthdawn”.
Nobody is going to defend the Palladium system used in “Rifts”. Not without copious amounts of alcohol, anyway.
Regardless, the question remains. Why play a bad system to enjoy a great setting? As a general rule, in my experience “Shadowrun” and “Rifts” are the primary examples here. Both have amazing and innovative settings, but their game systems are, well… trash, overall. “Shadowrun” is playable, as long as you homebrew the shit out of it, but “Rifts”? That’s torture, unless you break out the “Savage Worlds” edition.
Which brings up the next point. Since there is a better system for playing “Rifts”, why aren’t people using or homebrewing different systems to play other games? Well, we are!
For example, if you want to play “Shadowrun” without the core system, one can pick up “The Sprawl” and the free downloadable supplement, “Shadowrun in The Sprawl“. This is my go-to answer for playing SR without the system. Or you can grab the deluxe version of Kevin Crawford’s cyberpunk TTRPG, “Cities Without Number”… which includes rules for spellcasting and such. But if you really want an in-depth conversion, just combine the free editions of “Cities Without Number” and the free version of Crawford’s fantasy game, “Worlds Without Number”, which are wholly compatible in my experience.
Want to play “Earthdawn” without the system? Just about any fantasy TTRPG will do, if you carry over the setting books. Personally, I’d use Chaosium’s “BASIC” system, and bolt on fantasy elements from “Runequest” with cosmic horror from “Call of Cthulhu”, it should work just fine.
Love “Chill” but hate everything about it save the setting? Try “Vaesen”, or “Dead of Night”. The former is closer to the vibe of “Chill”, but DoN has the much better system.
Again, I could go on and on. With just a little homebrew goodness, you can swap over any setting into any other TTRPG system, especially those designed for universal play… except for GURPS, because it is just bad.