At Stoke: he got them up, kept them up, reached FA Cup final, and was far away from the club when it eventually got relegated. However, Hughes did something Pulis never did by getting them a top 10 finish, in fact he did it multiple times.
At Palace: he played perhaps the most attractive football of any of his sides and kept them up with a squad which is far poorer in individual talent than subsequent managers have enjoyed without moving them on from what Pulis did in the short-term. However, it was a short stay at that club.
At West Brom: they were heading for relegation during his last few months there however how much could he have done when senior players entered the front pages for "playing GTA" in real life. Oh and one of the pundits said West Brom were playing like they did under Pulis this year when they reached the play-offs so they haven't been able to get success and better football than under Pulis despite being several years on.
I would argue that Boro has been his only failure out of any of these four clubs.