I like something that feels like you have substance and choice that doesn't just let you break the game by equipping everything. I like how in FFT and its spinoffs you can pretty much craft your own supersoldiers by mixing and matching skills that you yourself pick to teach them, and it's still rarely totally game-breaking unless you go totally out of your way to grind those near-impossible job combos. I liked FFIX where you really couldn't use all of your passive skills at the same time - that gave weight to your choice and you had to adjust to each situation, because there was no one optimal ability combination that would let you win the game. The Witcher 1 probably has my favorite progression system in the entire series due to the points you get to distribute at every level not only being plentiful, but also divided into three categories, one for each skill tier, so each level up actually felt really meaningful and rewarding.