I'd say 00s is better than 10s in terms on impact. The main issue is that almost all 00s hits are focused in the first half of the decade, while 10s is better distributed during the entire decade. In terms of quantity of hits, I'd say is 50%-50%:
00s 1st half (2000-2004)
-Naruto and Bleach, specially Naruto
-Prince of Tennis, let's remember is the 3rd biggest spokon in sales. Almost the same length as Haikyuu, yet it has 15-20 more million copies sold.
-Technically Naruto and Prince of Tennis are 1999.
-Gintama in term on total sales and Death Note in terms of sales per volume (30-32 million copies sold with 12 volumes)
-Hitman Reborn and D.Grayman close the wonderful 2004 (30 million copies and 25 million copies respectively)
-The other hit of that period is Eyeshield21 which...is only at 20 million number.
00s 2nd half (2005-2010)
-2005-2007 period was weak. Yes, we had Neuro and Sket Dance, but their numbers are low. To Love-Ru would be the biggest hit of that period, with 15 million copies if I recall.
-2008 was a decent year with 3 hits, but which haven't had the same impact of the 00s 1st half or 10s manga (Bakuman at 15, Nurarihyon at 12-13 I think, Toriko at 20)
-2009 had Kuroko no Basket which is is the biggest hit of this entire period with 31 million copies. We got 2 more hits which are very known, but both Medaka Box and Beelzebub are at like 5 million copies.
10s decade
-2011: Nisekoi, it was the romcom of the period but sales are at 12 million if I recall
-2012 had actually 2 hits with impact: Haikyuu (40) and Assassination Classroom (28), and it also had Shokugeki which did as good as the second best hit of 00s 2nd half (20)
-2014: My Hero Academia (almost 30)
-2016: Kimetsu no Yaiba (already beating Bleach in total copies in Japan), The Promised Neverland (where is it now, 23?)
-2018: Jujutsu Kaisen
NUMBER OF HITS WITH 20 OR MORE MILLION COPIES:
00s: 9 (8 in first half, 1 in second half)
10s: 7 (not counting Jujutsu Kaisen)
NUMBER OF HITS WITH 30 OR MORE MILLION COPIES
00s: 6 (6 in first half, 0 in second half)
10s: 4
---
If we don't count 1999 as 00s and we count 2009 as 00s and not as 10 then situation is:
NUMBER OF HITS WITH 20 OR MORE MILLION COPIES (I'm going to count 1999 (Prince of Tennis, Naruto, and Hikaru no Go) as 00s and 2009 (Kuroko no Basket) as 10s)
00s: 7 (5 in first half, 2 in second half)
10s: 6 (not counting Jujutsu Kaisen)
NUMBER OF HITS WITH 30 OR MORE MILLION COPIES
00s: 5 (4 in first half, 1 in second half)
10s: 3