The recency bias is very strong here with quite a few posters, eh?
Usman is an amazing fighter and who knows what he's going to accomplish in the future, but to suggest that Usman is a superior version of GSP is wrong.
"Usman has 100% takedown defense, GSP has been taken down!"
There has literally been only a single takedown attempt (!) from an elite wrestler against Usman, which came from Woodley and has been defended.
GSP on the other hand has dealt with guys like Hughes, Koscheck, Hendricks, competing against some of those either with not much experience (Hughes) or in the twilight of his career (Hendricks).
"Usman is better everywhere"
Where do i start with that one...
Let's look at a few stats (UFC) alright?
... and let's keep in mind, that GSP's stats are like they are after a long career and after having fought elite competition for a long time, but i'll come back to that further below.
Significant strikes landed per minute:
Usman: 4.66
St-Pierre: 3.78
-> advantage Usman
Significant strikes absorbed per minute:
Usman: 2.33
St-Pierre: 1.40 (4th best in welterweight history)
-> advantage GSP
Significant strike differential:
Usman: 2.33 (2nd best in welterweight history)
St-Pierre: 2.38 (best in welterweight history)
-> advantage GSP
Ratio of landed to absorbed significant strikes
Usman: 2.0
St-Pierre: 2.7
-> advantage GSP
Significant strike accuracy
Usman: 54%
St-Pierre: 53%
-> advantage Usman
Significant strike defense
Usman: 58%
St-Pierre: 73% (best in welterweight history and 3rd best of all time across all divisions)
-> advantage GSP
Takedown average per 15 min.
Usman: 3.22
St-Pierre: 4.16
-> advantage GSP
Takedown accuracy
Usman: 47%
St-Pierre: 74% (best in welterweight history, 4th best across all divisions of all time)
-> advantage GSP
Takedown defense
Usman: 100%
St-Pierre: 85.2%
-> advantage Usman
Submissions attempted per 15 min.
Usman: 0.1
St-Pierre: 1.1
-> advantage GSP
Total fight time (welterweight)
Usman: 3:38:51
St-Pierre: 5:28:12
Submission wins / in brackets: submission wins in the UFC:
Usman: 1 (0)
St-Pierre: 6 (3)
-> advantage GSP
Totals:
Georges St-Pierre: 8
Kamaru Usman: 3
Things to keep in mind:
GSP has these stats after 5 1/2 hours of fight time inside the UFC, while having fought guys like Hendricks, Bisping (at 185) Hughes x2, Shields, Fitch, Koscheck x2, Penn x2.
Meanwhile, Usman has these stats after around 3 1/2 hours inside the UFC, having faced the likes of Covington, Woodley and Burns (i don't list Masvidal here, because i didn't include Condit in GSP's list, despite being a better fighter than Masvidal).
Out of these three fighters, there has been 0 takedown attempts from Covington, 1 from Woodley and 3 from Gilbert Burns.
Verdict:
While Kamaru Usman has a higher takedown defense percentage, more output and a marginally (1%) higher significant striking accuracy, St-Pierre trumps him in all 8 other stats, especially in terms of striking defense, where St-Pierre is amongst the most prolific fighters in UFC history.
This is even more impressive considering that:
a) St-Pierre's stats are those of a finished career, whereas Kamaru Usman only fairly recently has started to fight elite opposition and
b) St-Pierre has faced top competition (fighting champion Matt Hughes) after 7 pro fights, whereas Kamaru Usman didn't face a champion until having had twice the amount of pro fights under his belt.
Therefore, Georges St-Pierre remains the gold standard and the best welterweight of all time.
If a prime St-Pierre was to face a prime Usman, then i see St-Pierre winning the fight due to the wrestling of each other cancelling out (though i could definitely see St-Pierre landing reactive takedowns on Usman) and by being the better striker; exploiting Usman's porous striking defense.