Going to have to disagree about how you feel about Fat Sams ability. Annoying greedy fatty is bang on the money.
He's a good manager though.
He got Bolton punching above their weight for a long time and as soon as he went it all fell apart. I'd say he was the reason they were that high and not because of poor planning.
Newcastle - the guy never got a chance. Admittedly his "style" of football might not have been right for them but he got half a season and if the fans never wanted you, you are never going to last. Was par for the course with that newcastle side
Blackburn - again got them punching above their weight. As you say he got them 10th with a poor side. They went straight down as soon as he left which sums it up all really.
West Ham - This is his 1 "failure" of recent times if you had to say so. Even though his failure was to cement the spammers as a PL side. West Ham improved rapidly after he left (on the back of payet) but now still look a shambles harking back to Sams period after spending loads of money. I would say Sam did okay with them during this "failure"
Sunderland - managed to keep that shambles of a side up with some astute signings in the january window. Shame he left as i think Sunderland would have easily stayed up but Moyes managed to alienate all of Sams key players so they went down. Success
Palace - The FA cup finalist you described had 15 points out of 51 points. Big Sam comes in Dec, struggles a bit as palace have 0 confidence,makes some great january signings (hello sahko) and manages to keep palace up from 26 points out of 62 so another success.
Whether he can hack it at a big club is a different matter as he's never really gotten the opportunity but he's not a poor coach in anyway. Maybe his style (not that he's had the players to play a certain style, partly his fault for not trying) is what you like is a different point but he's got the ability.