Well, yeah, it's possible. Though this doesn't include something like World of Warcraft (nobody knows how much that's sold) or other games digitally distributed, Nintendo can dominate VGC's list.
14 PS2 - Grand Theft Auto: San Andreas Rockstar Games 18.16
16 Pokémon Diamond / Pearl Version Nintendo 17.36
17 Mario Kart DS Nintendo 17.35
23 Brain Age 2: More Training in Minutes a Day Nintendo 14.60 (outside shot)
25 Wii Sports Resort Nintendo 12.81
I left out the ones that will pass it up. On top of this will be NSMB Wii, Pokemon HG/SS, Wii Fit+. This brings San Andreas down to #21, so Nintendo needs 5 more 20 million sellers before 3rd parties come up with any. It's definitely possible.