Okay, reading this, I'll concede that he's more of a matchwinning bowler than the stats posted in this thread led me to believe. 5 and 6+ are not the same. My point is more to do with the value of these performances when considering an entire career though rather than the quality of the performances themselves.
No, it's not exaggerated. 11 of those sixteen five-fors were six wickets or more, compared to only 1 for Morkel and five for Anderson. He's almost single handedly bowled sides out for under 100 three times, something that is very rare these days, and has three seven-fors (Dale Steyn has one). And unlike Morkel, none of the were Zimbabwe. 'Only two ten wicket hauls'. It's not that easy taking ten wicket hauls (or eleven in Broad's case) , he's taken eight in a match nine times as opposed to Morkel's two, and Morkel has never taken ten. Considering how rare five-fors are you are silly saying that five more across the same number of innings is not noteworthy. You wouldn't begrudge a batsman who had made seven or eight more centuries than another over the same time (going by the respective frequencies of centuries and five-fors). The four wicket haul count doesn't include five fors (the fifties thing so passionately debated on here). Broad has taken four or more wickets in an innings 31 times opposed to Morkel's 26, and has taken more wickets on average in those four plus innings. The characterisation of Morkel as consistent and Broad as mercurial is well backed up by their career performances.
I'm not denigrating the accomplishment of 10 or 5 wicket hauls as individual performances as you seem to be interpreting it. They are really tough to manage. What I'm saying is that a disproportionate amount of credit is given to them when assessing the quality of a bowler across their career. Broad has managed them 2% more often than Morkel. That 2% is a great accomplishment of its own right because of the difficulty, but 2% is still only 2%- I will take better performance in the other 98% any day.
Morkel's 4 + 5 wicket hauls still outweigh Broads 4 + 5 accounting for difference in matches played.
I checked Morkel's stats. Half of his 5 wicket hauls came for 23 runs or less. I'm not sure about spells, but you can't bowl too many overs for so few runs, and you are shredding a side irrespective of whether this happens in 1 spell or more. Normalising for the difference in matches, these 7 compared to Morkel's 4 is 1.6 performances across well over 200 innings.