DS
1. Pokémon Diamond & Pearl - 1,289,151 connections*
2. Animal Crossing: Wild World - 302,669 connections
3. Mario Kart DS - 294,452 connections
4. The Legend of Zelda: Phantom Hourglass - 133,297 connections
5. Metroid Prime Hunters - 128,052 connections
6. Yu-Gi-Oh! Duel Monsters: World Championship 2008 - 119,709 connections
7. Ryuusei no RockMan 2: Berserk x Dinosaur/Shinobi - 116,549 connections**
8. Jump! Ultimate Stars - 73,217 connections
9. Transformers: Autobots & Decepticons - 69,572 connections***
10. Dragon Quest Monsters: Joker - 68,834 connections

* Pokémon Diamond - 758,303 | Pokémon Pearl - 530,848
** Shinobi - 62,604 | Dinosaur - 53,945
*** Autobots - 37,683 | Decepticons - 31,889 connections

Wii
1. Guitar Hero III: Legends of Rock - 984,889 connections
2. Pokémon Battle Revolution - 157,664 connections
3. Mario Strikers Charged - 148,971 connections
4. Mario & Sonic at the Olympics - 95,400 connections
5. Medal of Honor Heroes 2 - 85,392 connections
6. FIFA 2008 - 45,835 connections
7. Dragon Ball Z: Budokai Tenkaichi 3 - 34,255 connections
8. Madden NFL 2008 - 29,360 connections
9. Rayman Raving Rabbids 2 - 24,099 connections
10. Battalion Wars II - 15,623 connections

Games being tested
[WII] Mario Kart Wii - 4,840 connections
[WII] Super Smash Bros. Brawl - 2,800 connections
[NDS] Mario & Sonic at the Olympics - 1,643 connections
[WII] Pro Evolution Soccer 2008 - 378 connections
[NDS] Advance Wars: Days of Ruin - 39 connections

Source: Neogaf