What do you mean interested? Ryu is the generic wanderer hero
Ken is much less of a hero, he just goes around in his car boning chicks.
Plus Ryu has the whole evil counterpart which gives him plot importance.
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http://www.youtube.com/watch?v=7MwZfXy9mA4
http://osu.ppy.sh/stat2/shinytentacool-0.png