What I am getting at here is the Role of the Game Master and the Role of the system in encouraging or discouraging the players investment in characters. While I feel any system can provide great roleplaying experiences that will largely be up to the players at the table. The Game Master being primary of those.
Lets talk about system and how it can derail and drive players. The depth of a system needs to be global or players will often feel discouraged or even cheated. I have seen a Deadlands player utterly pissed that his gambling rogue creation was so limited compared to a Huckster. One was basically a skill based character and the other had skills and a complete magical advancement system as possibilities. Similarly when I have played Talislanta I have felt if you don't have access to magic the game is not worth playing. That would be fourth edition of Tal with all the modes of magic and whatnot. A system that rewards and denies like that can quickly change how players approach the game.
Flowing form this is reward. I think this falls on the Game Master pretty squarely. If you are not giving some experience reward for Roleplaying and character interaction, players will eventually navigate tackling the challenges that you do reward. This can also drive what players set as character goals. If you don't allow them to seek out and create the in world benefits they desire you are buffaloing them into some other game aspect.
Really the game should be a collaboration that is going to take some work off of the Game Master. If you are going to avoid player driven game plots you are taking a perhaps more well know approach but one that may be harder. I am really not judging here, I usually take the understood manual approach through the bushes in my life.