So playing a pre-defined character is roleplaying? How does that work then? Oh look I'm 'him' or 'her' following their pre-determined story till the end of the game. That's an RPG? You may as well watch a movie and save yourself the time.
Playing a pre-defined character (or characters) is certainly an RPG if (and only if) the character (or characters) happen to match who you want to play. That's exactly the problem with Western RPGs (so-called) regardless of the supposed offering of creating a character. The problem is, we cannot create a character we identify with because we are not offered sufficient choice in character creation. If there is no way to create a character you can identity and empathize with, there is no point in character creation at all and it's merely one more marketing bullet point (and a lie, at that, if it is stated you can create any kind of character... and it always is, even though that's a lie).
Your argument is also true for playing TES games and doing various quests. They are all pre-defined and you are simply playing through the quest story (which is almost always poor compared to a storyline in a game with pre-defined characters since such stories know what they have to work with and can be far more complex).
Aside from the many excellent Japanese games, consider a Western game such as Mass Effect. The writing in Mass Effect is far superior to any of the quests in TES games. However, you really don't have any choice in creating a character (i.e., there are no real aesthetic options to speak of and it doesn't matter what you choose, anyway) and all the other characters are already chosen for you. The overall story is very linear and predefined, too. As an RPG, it's pretty poor, UNLESS you just happen to want to play the kind of character that stars in the story (i.e., military officer in a sci-fi naval setting). I'll always prefer a Japanese game like Xenosaga over Mass Effect even though they have similar settings because I actually identify and empathize with the Xenosaga heroines, but I cannot identify and empathize with the Mass Effect characters.