Phew ... suspect I'll never understand your thought process ... he wouldn't be my first choice if I'm being honest but I couldn't possibly conclude as you have ... would appear to me that he earned the right to manage 'big clubs' by what he had acheived before ...
Cagliari 1988-91 takes them from Seies C to A with two succesive promotions
Naopili 1991-93 finishes 4th in Series A
Fiorentina 1993-97 Promted to Series A in first season and goes on to win the Coppa Italia and Supercoppa Italiana with them (2 meaningless cups ?)
Valencia 1997-99 Champions League qualification and wins Coppa del Rey (another meaningless cup)
Athletico Madrid 1999-2000 - admittely they got relegated - but they were going into administration that season so likely some mitigating circumstances
Chelsea 2000-2004 - pre Abramovic money takes them to 6th and a qualifies for UEFA cup in 2000-01. 2001-02 reaches FA Cup final (loses). 2002-2003 qualifies for Champions League. 2003-04 (Abramovic take over) they finish 2nd to Arsenal's 'invincibles' (highest finish in 49 years).
Valencia 2004-2005 wins UEFA Supercup beating Porto (who Mourinho had won Champions league with before leaving for Chelsea).
Parma 2007 joins Parma after their manager sacked and manages turnaround to avoid relegation
Juventus 2007-2009 finishes 3rd and 2nd in Series A (gets sacked during the second season

)
Roma 2009-2011 finishes 2nd to Mourinho's Inter in Series A and loses Italian Cup Final.
Inter Milan 2011 turned them around initially but they did fade later
Monaco 2012 - leads them to promotion to French top division after winning Ligue 2 title for the first time in their history ... 2013-14 finishes second in Ligue 1.
.. now personally that is one of the best managerial records I have ever seen - given that he acheived it over all those clubs - noticeably improving them all with the possible exception of Inter.