For me roleplaying is improvisation and storytelling with dice used to randomly determine the "gets" we receive during our scenes. So rather than an audience shouting out "Beach!" when asking for a location (for example) on an improv stage, when one of us makes the "offer" to the table (and DM) that we are going to attack the basilisk with our longsword, the dice are the ones shouting out "You hit!".
And thus... I want game rules and mechanics that are most aligned to the narrative reasons we are asking for this unknown "get" for whatever game we are playing. If there are mechanics that don't facilitate the story, then there's no reason to have them. One easily understandable example is the Call of C'thulu d20 game... this is a genre, setting and story that is meant to be a bunch of completely normal people slowly discovering these eldritch horrors all around them, losing their sanity as their brains cannot comprehend them while they try to survive, and then probably dying-- and yet the d20 system has experience points and levels to become more powerful characters. But becoming more powerful and "leveling up" is the exact antithesis of the narrative of how Call of C'thulu is meant to play. And thus those mechanics are bad mechanics in my opinion because they do not serve the story that we are trying to tell as we sit around the table.
And that's often the problem with a lot of "generic" game systems... they may allow for multiple genres and settings to use one set of rules, but a lot of those genres and settings have a specificity in their stories that demand specialized mechanics for them. FATE is not the right system to do "monster hunting", D&D is. The genre emulation we get from the Fiasco playsets is not helped by creating characters using the HERO system. The tension of the Jenga tower is exactly the "get" you want for Dread, but it doesn't serve us in the Space Fantasy of Star Wars.
So to me... figure out what you want the game to feel like and offer up as variables to the players as they all create the story at the table, and then design rules and randomizer systems that help highlight them as much as possible.
And thus... I want game rules and mechanics that are most aligned to the narrative reasons we are asking for this unknown "get" for whatever game we are playing. If there are mechanics that don't facilitate the story, then there's no reason to have them. One easily understandable example is the Call of C'thulu d20 game... this is a genre, setting and story that is meant to be a bunch of completely normal people slowly discovering these eldritch horrors all around them, losing their sanity as their brains cannot comprehend them while they try to survive, and then probably dying-- and yet the d20 system has experience points and levels to become more powerful characters. But becoming more powerful and "leveling up" is the exact antithesis of the narrative of how Call of C'thulu is meant to play. And thus those mechanics are bad mechanics in my opinion because they do not serve the story that we are trying to tell as we sit around the table.
And that's often the problem with a lot of "generic" game systems... they may allow for multiple genres and settings to use one set of rules, but a lot of those genres and settings have a specificity in their stories that demand specialized mechanics for them. FATE is not the right system to do "monster hunting", D&D is. The genre emulation we get from the Fiasco playsets is not helped by creating characters using the HERO system. The tension of the Jenga tower is exactly the "get" you want for Dread, but it doesn't serve us in the Space Fantasy of Star Wars.
So to me... figure out what you want the game to feel like and offer up as variables to the players as they all create the story at the table, and then design rules and randomizer systems that help highlight them as much as possible.