Yes, Lost World like 700k , Mario and Sonic probably didn't do very good either.
But there are examples of "bad" Sonic games doing well on other systems, Secret Rings, 2006, Black Knight,Sonic Heroes, Shadow the Hedgehog, Sonic Unleashed, etc.
Im not saying that AC are bad games however, just that sometimes a low quality/dissapointing title can sell if it has something going for it.
There are Mario games that sell too even if they are very mediocre, like NSMB 2 or Mario Party ds, or Call of Duty Vita, that was a disaster.