I've played both, and let me tell you, the similarities are negligible. The Service Rifle is an old M-16 prototype, and the Assault Rifle is based upon the FAL, and has been there since Fallout 2. The Chinese Assault Rifle is based upon the AK-series, and if we're going to split hairs over copying other games' guns, then both copied it from Counter Strike (if not an earlier game).
All the melee weapons in New Vegas are either completely unique or in the case of the combat knife, ubiquitous. The minigun is older than CoD, and the rest of the Big Guns are unique. The Marksman Carbine is also ubiquitous, it is a development of the M4 series.
The weapons are completely different, and the similarities exist only exist in weapons that go back to DOOM or Counter Strike. You won't find any nuclear bomb catapaults in Black Ops, and the FAMAS is certainly not included in the Fallout timeline.
-Penguin