If you mean how high a single platform managed, then enrageorange just linked the best.
1. DS w/e 20th Dec 2008 with 2,114,585
2. DS w/e 22nd Dec 2007 with 2,043,008
3. DS w/e 26th Dec 2009 with 1,855,412
4. Wii w/e 26th Dec 2009 with 1,843,614
5. 3DS w/e 24th Dec 2011 with 1,786,398
6. DS w/e 27th Dec 2008 with 1,778,002
7. Wii w/e 19th Dec 2009 with 1,763,754
8. DS w/e 19th Dec 2009 with 1,741,057
9. DS w/e 15th Dec 2007 with 1,737,070
10. DS w/e 13th Dec 2008 with 1,699,385
Now although we can't view PS2 sales anymore, I remember checking them and it's highest week was either ~1,670,000 or ~1,770,000 so it should fit in somewhere between 7th and 11th... I think it also had 2 weeks in the 1.4 million range, 2 in the 1.2 million range and one in the 1.1 million range... but that was it, only 6 total weeks over 1 million, and only once was it 2 consecutive weeks over 1 million (whereas DS managed 5 consecutive weeks over 1 million in 2008 alone)
If you mean total hardware in a single week then without being able to see PS2 it's hard to tell, but I would hazard a guess at 2008, which got to 5,959,914 w/e 20th Dec and the PS2 was still going ok then so probably added 300k or so. Or possibly 2009 which got to 6,049,399 plus whatever the PS2 did.