Selling less of a sequel (less than half as many units on Xbox? not sure of the exact figures) when you clearly spend a lot more marketing it is a failure, yup.
Say you rent a market stall for 3 months and sell cheese, and make $10,000 dollars in the first month.
Next month you spend some of your profits on a bigger stall, and more people know about it, but you decide to change the type of cheese you sell and the quality. You make $4,000 that month because people turn up to the stall and don't get what they wanted, telling other potential customers about their disappointment.
I'd consitute the 2nd week as a massive failure in the context that if you'd set up a bigger stall BUT with the same cheese you'd have made far more money AND made more customers happy.
Now, in the third month... do you go back to the month 1 cheese type and quality, or do you hope that people start liking your month 2 cheese?