I was specifically referring to D&D4e, though I suppose the new d20 version of Star Wars is applicable as well, where ones character is really defined by ones powers. As an example, if someone were to create an archery-based ranger, it would likely be virtually identical to a ranger with the same theme created by someone entirely different.
Roleplaying is the burden of the individual and its lack thereof is the failure of the player and not the game they are playing. Saying certain systems stiffle or eliminate roleplaying altogether is a fallacious(It means logically unsound or deceptive ,and not fellatio pervs.....) statement. You can roleplay a Monopoly game if you so desired(look, I was drunk and bored and when you combine the two with me stuff happens,I just hope the video doesn't still exist). However, I do agree that Fate is a vastly superior system that encourages that play style and allows players ,through aspects, to take a more active roll in the molding of the story. In 4e yes you could have two different archery based rangers that have alot of overlap in terms of their powers, but as you so succinctly put it the powers don't matter for the purely roleplaying aspect of the game, so if they don't matter then how they play the characters is what is the most important thing. All I am saying is when you get down to it a roleplying game is an environment that encourages communication, creativity , and just good old fashion down home fun.I personally look at games like 4e as an occasional cathardic release, you have long campaign highly cerebral with twists and turns and genuine emotional tension where there is a lvl of creative exchange between storyteller and player that just doesn't exist in other medium,taking a break and rolling thog the barbarian and smashing goblins with your mighty thews, can be a nice change, but also can be an enriching roleplaying experience as well,if you allow it to be.