I have to say CoD4, WaW veteran was much more easier. But CoD2 and CoD3 were behind CoD4 by not too far. Mw3s veteran was just stupid easy, it wasn't worth calling veteran actually I managed to get all the intel, all the misc achievements and the campaign ones in one play-through on veteran. Mw2 has its moments but is pretty easy too. Black ops was quite difficult multiple maps needed to be redone. I want to see how Black ops 2 will be, since it's made by Treyarch hopefully it has some difficulty too it. Activision just sucks at making games..
2000th Acheievement - 8.12.2013 - Dead Space 2
- Skewered in Space 15
40002 Gamerscore - 8.14.2013 - Midnight Club: LA
- Unicycle 20