Part of the problem here is that the character Kyon is actually a bit of a riff on the archetype of Yuuichi (as he is portrayed in the game). Rin also being a bit derivative of that stereotype. Sugita happens to play that role well, which is both helpful and damning -- I kind of view his role as Yuuichi as "comiing home to the source"
Fortunately, he is capable of playing other sorts of personalities though I can't pull his credits out of my head at the moment.
I guess my best advice is to remember this is old material and many later series riffed off of many of its elements to try and grab some glitter.