Sales don't always indicate the health of a franchise though. Sonic Unleashed, Sonic Heroes, and even Sonic 06 have sold more than Sonic 3 ever did for example yet those games are generally reviled. Sega might have made a quick buck with their cheap and shallow Shining games, but they've paid for it by weakening the brand substantially.
Don't think it's fair to lump Heroes with the trainwreck that is Sonic 06. That hurt the brand massively but you don't end up selling 6 million copies of a game (Sonic Heroes) if said title was responsible for killing people's interest in a series.
Though Shining's sales were definitely killed off in the West because they were pandering heavily to Japan, that being said I can't say wither the series was a decent seller here or not. Probably should keep in mind SEGA always make money off of the figures each game promote, so it's not solely about software sales anymore.
Also to be fair in this discussion, Sega DID make a SRPG called Shining Force Feather for DS. It just never was released internationally and as far as I know died a quiet death back home in Japan.
who knows why it didn't catch on.
It was also the worst selling Shining game in Japan since the original Shining remake for the Gameboy Advance.
Sales of Shining games in Japan
Shining Ark - 83,641
Shining Force 3 - 67,516
Shining Force III Scenario 3: Hyouheki no Jashinguu - 38,382
Shining Force III Scenario 2: Nerawareta Miko - 37,592
Shining Soul - 72,997
Shining Soul 2 - 13,928
Shining Force: Dragon's Revival - 34,794
Shining Tears - 104,762
Shining Force Neo - 96,013
Shining Force Ikusa - 130,763
Shining Wind - 126,561
Shining Force Feather - 67,341
Shining Hearts - 162,885
Shining Blade - 161,868
Should be noted that the one two failures of Shining Soul 2 and Shining Force: Dragon's Revival gave Sawada the opportunity for Tony Taka to be brought in for future games and the failure of Feather killed any chances at the series moving back into the SRPG realm.