I've read that Sparking Neo and Meteor were multiplatinum (2m+) sellers, but I've never found a source for that. People usually cite VGChartz (which is unreliable) and Wikipedia (which doesn't have any sources, either).
In Japan, each of the Sparking games sold over 500k on the PS2 according to the DBS 30th anniversary guidebook. Apparently, Sparking Neo and Meteor didn't sell well on the Wii in Japan, since their sales on that platform aren't listed (for the record, the first Sparking was only on the PS2).
How much did they sell in the US? I recall that the Wii version of Sparking Meteor became very rare, so I guess it didn't sell well on that platform.