I'm very much in agreement with the other posters pointing out here that:
A) Both CJ and JR were 'starter quality' QBs last year, AND both are this year.
B) CJ's numbers were not all that great last year (marginally lower than but comparable to JR's) and he HAS made significant improvement to his game this year (that can be easily seen looking at his QB ratings in starts last yr vs this yr).
C) JR 'won' the starting job at Michigan, with a former NFL head coach and big-name college QB as the head of that program - if JR wasn't clearly the best option for them to win now, it's guaranteed that Harbaugh would bench him and start playing his younger guys, planning for next year. JH thinks he can win THIS year with JR as his QB - end of argument (if he benches Rudock for his younger guys, we can have the discussion about JRs capability as a starter, but he's 3-1 right now for a near-Top-25 team).
That said, CJ busted his ass TRYING to win the starting job from JR - he didn't just sit back and get comfortable as the #2- he WANTED the #1 job and was willing to work hard to show the coaches he deserved it. And he eventually DID that. His work ethic and willingness to be a team player while busting his butt to improve his own game is something that gets infectious among teams - the higher level of play you are seeing from receivers is due to that mentality and work ethic. And that is probably something else Ferentz and the coaches saw in him. CJ expects our wides and TEs to catch the ball if he delivers it close to them - he expects them to make adjustments on the ball to get to it - he expects them to fight the DBs to 'win' the ball when he threads too narrow a window. And they've also bought into the work ethic and that fight to win every ball. That's probably why they are dropping fewer passes - they've put in the work, too, to catch 100% of what comes within arm's reach of them.
I think CJ is demonstrating he may be a better team leader and uniter than JR was, but Jake is not a slouch as a QB - making it as a starter for 2 major college FB programs is nothing to sneer at. I love seeing Michigan lose, but I don't root against Rudock, because he busted his ass for the Hawks, too, when he was here. I do think CJ has a higher ceiling that Rudock, but we'll see as this year plays out.