I agree and yet disagree.
Vita is billed as console gaming on the go. It's supposed to be a portable PS3-lite. In that respect, critics have every right to rip it to shreds because even if it was on 3DS this would be a disappointment (although, more expected and tolerated).
If they can make faithful CoD ports to Wii, they could have made one for Vita.
not to mention its not like the COD DS games got great reviews themselves, and the last few have sold like crap