I was talking about this with my Juventus supporting friend yesterday. Basically I feel like a book on "all time greatest managers" would have be divided into several sections. For me at least, I can't just judge "greatest" as "Big trophy winners". I mean if winning Big Ears is a requirement to be great then someone like Di Matteo ranks higher on the greatest managers than not just Wenger but people like Shankly, Lobanovskyi, Bielsa, Rangnick, etc and that just doesn't ring true for me.
So we thought you'd really need 3 different categories to judge great managers although admittedly some fit equally into more than 1 category like Michels or Herrera.
Most Successful: Michels, Ferguson, Clough, Mourinho, Paisley, etc
Tactical Innovators: Chapman to Bielsea, to Rangnick.
Club Builders/Developers: Shankly, Wenger, Herrera, Lobanovskyi
While I have a lot of problems with Wenger's faults of the last half decade and in general, I think few managers have really built a club up like he has even if his philosophy has inherent weaknesses. I was reading an interview with Dragan Stojkovic which was interesting because Stojkovic discussed how much Wenger influenced him "I started to understand tactical behaviour. I started to understand modern football. As a result of that, in 1995 he became J. League manager of the year even though we were only second, and I was player of the year."
although he did leave this interesting quote from 2011 about Wenger and Van Persie incidentally.