I think their point is more that Sonic Adventure was the last real sonic game. I'd agree with that. Since then we've gotten: Sonic Shuffle, Sonic Adventure 2, Shadow, Sonic Heroes, Secret of the Rings, 'Sonic The Hedgehog', the horrible GBA games, Sonic Riders, etc etc
Specifically since the Dreamcast went down, Sega has gone out of their way to $#@! out the Sonic franchise.
If not Sonic Adventure, maybe the NGPC or NGage games would be the last real sonic games. I think it has to do with the fact that those two platforms were Sega endorsed, or related or something (not sure the term).