IMO Treyarch never quite nailed the visuals the way IW did. Since they share tech, it's gotta be their artists and designers. On the other hand, I much prefer Treyarch's audio design...although BlOps2 takes a step backward on the weapon sounds. The AK-47 and Galil both sound worse than their BlOps1 incarnations. Of course, COD doesn't hold a candle to Battlefield in the audio department to begin with.
Here's my short review:
The campaign is the best of the series, with the possible exception of WaW (which I adored). They did a great job of addressing the complaint that BlOps1's campaign was far too on-rails, with too-constrained pathways, and taking control away from the player too often. BlOps2 makes sure you have plenty of bad guys to kill and plenty of space to kill them in. I really dug the "choose your own adventure" aspect, too. Unfortunately, Strike Force missions are as terrible as everyone says they are, and they become unplayable at the highest difficulties. If you want the best ending, play it on Recruit. I loved choosing my weapons, perks, and grenades at the start of a mission. This is a fantastic addition to the series. Overall, this is the most fun I've had in a FPS campaign since Crysis 2.
Multiplayer to me is a mixed bag. The Pick-10 system is great. The weapons are fine, consisting mostly of things that are either real (AN-94, SCAR-L, Skorpion Evo 3, etc) or exist as a prototype or on a drawing board somewhere. It's still COD, not Halo. Shotguns are now usable, since their magazines have been significantly increased and have a greater variety of useful attachments available. I really like the bots being able to play Domination now, and there's deep customization for private matches.
To me, the biggest problem is that Treyarch has gotten obsessed with stopping camping. It's just idiotic---as long as you make maps with walls and cover, some people will hide and ambush the players that like to run around. This has been part of FPSes since Doom. Ghost no longer works unless you're moving, i.e., it's solely for not being noticed as you flank rather than helping you hide. The senor jammer, camera spike, and motion sensor are gone. Most of the maps are small, with short sight lines and no open areas. They're clearly designed to make you run around and test your twitch reflexes against each other. Nuketown is about mid-sized for a BlOps2 map. There's certainly nothing like COD4's Overgrown or Strike. And then you've got the Millimeter Scanner, which is basically a wallhack for spotting non-moving enemies around corners, and the Target Finder, which highlights everyone in your field of vision with big red diamonds. And it seems to me the recoil's been greatly reduced since BlOps, with guns having a more MW2-like feel. There's a lot more hand-holding for spastic preteens who can't control their rage when they get killed by someone they didn't see.
Basically, the game feels like they're catering to a specific type of whiner that feels like it's not fair that he got killed when he ran headlong into a room without tossing in a flashbang first or checking his corners, or that a game is "broken" if he ran down the same road six times and got killed by the same sniper six times. I don't expect COD to be a tactical shooter. But the new obsession with preventing people from using anything remotely resembling a realistic tactic is just a little ridiculous.
