He's just somewhat tactically naive and has made some horrific signings lately - Lovren and Balotelli being the obvious two. But he has turned Coutinho and Henderson into top class footballers who would probably get into any side in the Premiership. He seems to be decent at working with younger players.
I don't think Benitez would necessarily be doing any better given the talent and spending power the top 4 have, and Codgson definitely wouldn't.
If eventually he becomes England manager (as he seems to have been tipped for despite being Northern Irish) he will likely do a lot better than the current and recent incumbents.
Tactically very poor and has no plan b. Got shown up in the CL and is out thought by masterminds like sherwood & pulis.
Found latest formation by chance and they kept clean sheets by good fortune. Proven unable to buy a decent centre half or striker (studga aside) and plans his transfer strategy very very badly (although the panel shoulder part of that blame).
The year after Rafa lost the CL his went out and bought Torres ... the year Buck misses out on the Prem he goes in for Lambert.