Cal is an elite recruiter (ethical or no) that ends up with way to much turnover year to year. He'll have years where they are elite NC contenders and others that just fall apart in the NIT.
There will be to much inconsistency to prove his coaching credentials one way or another - he'll be forever a by-product of his players talent - not his.
I think the first sentence here is an interesting point. JB is in some sense the ultimate low-variance coach - always winning seasons, relatively few spectacular ones (at least till recently). Calipari is somewhat of the opposite, as we've seen the last two years. (Although JB also went to the NIT the year after playing for the NC in '96.) I'm not sure this makes JB a better coach. Calhoun also had a style that produced huge variances - a lot of NIT bids mixed in with a lot of absolutely dominant teams. And I think Calhoun, while a jerk, was obviously a great coach. Someone like Tom Izzo is more on the Boeheim end - very, very good teams year-in and year-out, but he's not a guy who's going to have a wire-to-wire dominant team. But Izzo's still a great coach (now, probably #2 to K).
On your second sentence, I don't see how you can ignore recruiting when evaluating a college basketball coach. It is probably the most important part of a coach's job. And if you do insist on ignoring recruiting to evaluate whether a coach is "great," I'm not sure how you do it -imagine a counterfactual where everyone has the same players?
I think Calipari is a scumball and bad for college basketball. I think he's probably cheating more than average, but I also think everyone's cheating at least some. But I think you can make that point without making the weird argument that he's not a good coach.