Okay, bear with me.
The point of Ryu is that he is everything the others aren't. He has no particular quest, even back when Gouken was dead he didn't particularly care to hunt down Akuma. He doesn't care for fame (SF2 ending) or money or anything very much but his own improvement. In that way he embodies the romantic ideal of the samurai spirit, and through that the Japanese ideal. He's unburdened by distractions so he can focus entirely on his art. He has friends that he cares for but he's not tied down by them. He's ascetic, righteous, chaste, generous, basically friendly to anyone unless they wrong someone. He has a philosophical side seen in many win quotes, and he often encourages others to better themselves even if he is too humble and too preoccupied to actually take a student. He is very much a Musashi Miyamoto (who is the quintessential samurai stereotype), just without the sword.
I know quite a few martial artists and it seems that being dedicated to a martial art tends to give you those qualities. It would be very out of character for him to be petty or angry or vengeful. His only flaw is the trap they introduced through "magic" with Satsui no Hadou, but this was just to add some drama. Because someone who lives happily doing his thing will have very little actual drama. By nature he won't drive a plot, but he can still be drawn into it simply be being an extraordinary human that others want to use for whatever purpose.
It's actually more common to deconstruct an archetype nowadays, so I appreciate that Ryu is actually genuine and that they closed the door on that Evil Ryu crap. He is still interesting.
