I know you didn't ask me, but I'll jump in while I'm waiting on pizza...
Interesting questions. I think most of us aren't truly qualified to know who is actually a really good OL coach or not (probably true for most other positions as well). I tend to look at who has generally had good OL play, who is at programs that can run the ball, who has moved up in the profession, who is not only getting guys drafted, but having those players either star or make it for awhile in the pros, and who is getting good recruits.
Matt Luke would have probably been number one on my list the last couple of years. Besides him, Bill Bedenbaugh at OU seems like a really good OL coach. Brad Davis at lsu too. And Stacy Searels at Georgia. Highly doubtful any of them are coming- less doubtful than Luke.
Out of that quartet mentioned earlier, Rudolph seems to be the one that checks most boxes. I'm sure there are others out there as good as, or better, than Rudolph. I can't necessarily say who, off the top of my head though.