I see a lot of games being judged on how well they let us tell stories, or simulate an environment, or how satisfying their risk-reward mechanics are - but I don't see much being said about the roles we play in roleplaying games.
Although I find it hard to quantify exactly how it's achieved, I relish a game that really lets me get into a good role. To embody a character. Some of my best gaming experiences were all about being someone else, doing something else in a sustained and rewarding way, often regardless of whether a satisfying narrative was produced in the end. I think many of us have fond memories of that one character who it was fun to be despite the campaign's senselessness. Roleplaying can be it's own reward, surely, even if the G in RPG isn't functioning quite right.
Sometimes it's in the details. I find it easy to get into character when playing the Warhammer Fantasy RPG and being given colourful but fairly useless items in my pockets during character creation. It really helps me understand who this unlucky peasant is and how I could play that role.
Sometimes it's in the broader setting. Characters in Paranoia don't tend to be very complex but the richness of Alpha Complex presented in the right way makes getting into the headspace of a violent batch-clone in the service of a terrifying regime deeply rewarding.
Sometimes it's in the play-space. The rush to invent and position characters in relationship webs in collaboration with other players during the opening rounds of Fiasco seems to help solidify satisfying roles.
What RPGs give thought to helping players get into their roles? I feel many assume this is just a thing that happens: "You're X, now lets talk skills and abilities." Is getting into a role something that roleplaying games consider, or just a given? Is role-playing an end in its own right, or just colour?
What options are out there? What RPGs, or subsystems of RPGs, help you to be someone else and live out a role?