The numbers are starting to come in, and while DmC is currently the best selling game in the UK (knocking out FIFA), it's barely managed to sell over a third of what DMC4 did in the same launch window. Although we won't know the exact numbers until anyone but Capcom themselves releases them, that won't be for several months. Wonder how the sales will be in the US since this game had an estimated 180,000 preorders across both systems before it released, but between this and DmC getting knocked out of the top 100 on Amazon (while the HD collection is still on there, mind you) so far it's not looking hot.
EDIT: Japan sales are in, DmC sells 1/2 of what DMC4 did in its first week
DMC4 came out on a Friday in the UK and Japan as well, giving DmC a three day headstart for its opening week and it still underpreformed. All we're waiting for now are the US sales, which probably won't be announced until February.