For January we had:
1 DS: 64.500 (90%)
2 PS2: 59.000 (90%)
3 PSP: 40.000 (90%)
4 PS3: 37.000 (90%)
5 X360: 19.500 (90%)
6 WII: 9.000 (90%)

and for February:
1 NDS: 58.000 (90%)
2 PS2: 31.000 (90%)
3 PSP: 30.000 (90%)
4 PS3: 22.500 (90%)
5 WII: 15.500 (90%)
6 360: 10.500 (90%)

As we can see all consoles but Wii went down. NDS by 10%, PSP 33%, PS3 39%, PS2 47% and X360 46%. Wii is up by 72%!!

Is good performance for Nintendo consoles due to supply constrains in January?

It's possible, but I haven't heard of any supply problems in Italy. Maybe Wii can catch 360 this year, but with 360 price cut and GTA IV it may lose some ground next few months. I don't know how Easter affects sales in Italy, though. Christmas saw a big boost for Wii hardware, so it's possible we will see another boost in March if Italy is anything like the UK.

 Italy hardware march GFK

week ended March 09
1 Wii

2 PS3

3 360 

week ended March 16
1 Wii

2 PS3

3 360 (+55% price cut )

week ended March 23
1 PS3

2 WII

3 360 

week ended March 30
1 PS3

2 WII

3 360 

prosugno, you don't have the software numbers for the week ending 20 april?

May 4 software  week 16 and 17

Italy
Hardware
DS Sold Out (90% of the shops)
Wii Sold Out (90% of the shops)

360
Arcade: Sold Out (90% of the shops)
Pro: Sold Out (70% of the shops)
Elite: No Sold out

PS3 No Sold Out


Software
Wii
Mario Kart Wii Sold Out (90% of the shops)
Wii Fit Sold Out (90% of the shops)

Grand Theft Auto IV
360 Sold Out (90% of the shops)
PS3 No Sold Out

www.gfk.it

Software seems like it's spurred hardware demand, although it's difficult to know how much supply Wii & 360 had anyway. Microsoft will lose a lot of potential sales to PS3 due to lack of 360 & GTA IV 360, they need to restock quickly. April hardware sales should be very interesting, pity we have to wait so long, though.

The guy who posts the GfK data on the Italian forum says that for day one 100k units were shipped for PS3, and 60k units were shipped for 360. The target for PS3 version is 200k in 2008.

Link 

'sold out' doesn't mean much if you don't know how many consoles were available; so the 360 arcade and pro are sold out, but how many were there in the stores? sure less than the PS3's..

Italy, week ended April 20
01 Mario Kart (WII) [16.850]
02 GT 5 Prologue (PS3) [7.600]
03 Cooking Mama 2 (DS) [4.200]
04 Mario & Sonic Ai Giochi Olimpici (DS) [3.650]
05 Brain Training (DS) [2.850]
06 Cooking Mama (DS) [2.550]
07 Pro Evolution Soccer 2008 (PSP) [2.500]
08 Pro Evolution Soccer 2008 (PS2) [2.450]
09 God Of War Chains Of Olympus (PSP) [2.250]
10 Euro 2008 (PS3) [2.100]

Italy, week ended April 27
01 Wii Fit (WII) [45.500]
02 Mario Kart (WII) [10.750]
03 GT 5 Prologue (PS3) [4.500]
04 Cooking Mama 2 (DS) [3.900]
05 Mario & Sonic Ai Giochi Olimpici (DS) [3.850]
06 Brain Training (DS) [2.850]
07 UEFA Euro 2008 (PS2) [2.800]
08 Pro Evolution Soccer 2008 (PS2) [2.650]
09 Pro Evolution Soccer 2008 (PSP) [2.500]
10 New Super Mario Bros (DS) [2.100]