I'm sure the article means worst-performing MAJOR Sonic launch ever, as I doubt Sonic Drift or Labyrinth did well.
Anyway, I wish SEGA wouldn't try to reinvent the wheel with every Sonic game. They had something great with Sonic Colors and then Sonic Generations, and then they threw that away for Sonic: Lost World. Now, while that game isn't horrible, the mechanics weren't in tiptop shape and the game progressively got worse as you played through it (a trademark Sonic Team thing, the first level being the most polished and things drop off eventually from there).
I played both of the Sonic Boom games, and I really saw some potential in the Wii U game. However, you could tell the game was rushed to coincide with the release of the cartoon. It's a shame because with more time the combat could have been much better, the glitches wouldn't be so apparent, and the other problems plaguing the game wouldn't be so numerous.
The 3DS game was a fun diversion, but it was way too short for the asking price of $40. That's just a ridiculous asking price.