The only ad I saw was a two-page advert with an overdosage southern accent.
Sure, there were lots of reviews, but that usually doesn't help much. Even though the ratings were great, it just will not convince many to buy it.
Also, the the number of fans.
Oddworld lost fans when MO came out, did they not? Also, the PS2 plans had to be cancelled, causing a lower chance of high sales. We also have to consider the size of Oddworld's fan basis. How many fans do they have? How many are willing to purchase an X-Box to play their games?
That was a rumor, and has not been confirmed as of yet.