Did some googling and stumbled upon some data compiled at NeoGAF about gundam sales in both DS and PSP
NDS:
233,483 SD Gundam G Generation: Cross Drive (Bandai) (8/9/07) - through Oct 7/07
94,317 SD Gundam G Generation DS (Bandai) (5/26/05) - through Nov 12/06
18,339 Kidou Gekidan Haro Ichiza Gundam Mahjong DS: Oyaji nimo Agarareta koto nai noni! (Bandai) (12/29/05) - through ??? (between Jan 8/06 - Oct 15/06) (MC)
16,545 Kidou Gekidan Haro Ichiza: Gundam Mahjong + Z: Sara ni Deki Ruyouni Nattana! (Bandai) (9/6/07) - through Sept 9/07 (MC)
PSP:
278,702 SD Gundam G Generation Portable (Bandai) (8/3/06) - through Sept 2/07
188,374 Gundam Battle Chronicle (Bandai) (10/4/07) – through Nov 11/07
131,742 Kidou Senshi Gundam Seed: Rengou vs. Z.A.F.T. Portable (Bandai) (4/5/07) – through Sept 2/07
114,861 Gundam Battle Royale (Bandai) (10/5/06) – through Dec 31/06
73,275 Gundam Battle Tactics (Bandai) (9/22/05) - through Dec 25/05
52,887 Kidou Senshi Gundam: Giren no Yabou- Zeon no Keifu (Bandai) (8/11/05) - through Dec 25/05
42,097 Quiz Kidou Senshi Gundam: Monsenshi DX (Bandai) (7/13/06) – through Dec 31/06 (MC)
source:
http://www.neogaf.com/forum/showthread.php?t=177723