Both are overrated honestly.
Wait, that ain't true.
Halo is fine, personally, I think that the series would highly benefit from being made for PC, not for outdated consoles.
All of the negative feelings I've had for Halo was because of Microsoft being douches and because, while the game is fine, I never understood the HUGE popularity it has.
So yeah, fine game.
"Game of the year, 9.4/10"? Not really, but still a good game.
Black Ops 2, just like Black Ops 1, has it's own set of positive and negative aspects, when compared to Modern Warfare 2 and 3. I enjoyed MW3 and I personally thought that it was an improvement over MW2 and BO, despite it's flaws. It's too early to judge BO2, really.
Oh and now you are saying that Reach was awful, yet that Halo 3 was great. Eh. They look exactly the same to me AND I've heard very positive things about Reach.
Get Resistance 3 if you have a PS3. If you have a PC, get Doom 3 BFG/or if you want multyplayer, play Blacklight: Retribution.
If you only have XBOX 360, get Halo 4.