Ryu can kill just fine, and the definition of a meteor smash in 4 is by the crash sound effect. Ryu's dair makes this sound in the air, so it is. He doesn't really have much trouble killing from what I've experienced, and down B isn't a counter in the traditional sense. He blocks one attack (taking no damage), and further attacks will knock him out of it. One thing you should make note of, however, is that you can REVERSE the punch just like Falcon and Dorf.