In no particular order:

AD&D, as implemented in Baldur's Gate II (and retroactively in Baldur's Gate Enhanced Edition) - I liked how each class was unique and though the class/race restrictions were a bit unfair and favored the taller races, it made them unique from a lore perspective. Also, each decision mattered - dual-classing carries a lot of benefits, but choosing the right moment for it can take some work. Customizing mages comes down to learning from the scrolls you find, but whether you can learn it still depends on your stats, so it's fun.

Tactics Ogre: Let Us Cling Together - I find it really interesting that jobs level up independent from a character, so if your fighter is level 14, any other character that becomes a fighter is immediately a level 14 fighter. This doesn't mean they'll all be identical, though - each job offers a whole pool of skills that an individual character may learn, so you definitely have tons of room to experiment and specialize particular units, so no two fighters can ever really be the same unless you really grind hard or make them the same on purpose.

Bravely Default - FFV's job system on steroids. Aside from an always-on passive action and a range of learned abilities, each job can also take on the actions of another job, and up to five passive abilities from other jobs. Goes really deep and you can make some really devastating combos - and the best part is the endgame bosses really require you to get clever with your skillsets. Too bad Bravely Second totally broke this system and made it kinda flatter despite offering more variety.

Final Fantasy Tactics - love the way you accumulate job points not just by being a certain job, but also by being around people with another job. How jobs unlock other jobs later on is also pretty cool, and it was super fun building a character from scratch by jumping all around the job tree.

Final Fantasy Tactics Advance - pretty similar to Tactics, but with the added variety of races, which was really fun. And though the FFIX ability system implemented here is controversial to many, I liked it a lot. Looking for specific weapons to make my character cooler was part of the experience.