Black Ops II is something CoD hasn't been in years - it's actually great!
Technically, Black Ops II looks aged, sure, but it runs pretty damn great at least (as it should considering the age of the engine). I did see some improvement in the lightning and reflections, so there appears to be some use for the DX11, even if it isn't much. Sound quality is so-so for the guns. They don't sound nearly as good as those of BF3 or MoH, but they sound pretty good for a CoD game at least.
The campaign is one of the best in years, perhaps even the best since the original MW. There's lots of variety in the locations, cool setpieces, and above all: some actual backstory for the characters and villain, as well as several important choices the player gets to make that changes how the story plays out, giving the campaign great replay value.
Zombies is back as usual, but I never really cared for that, so I won't go into much detail. At all. Moving on now.
MP has seen some great changes. The Pick-10 system is fantastic and feels very balanced, giving you more customisation options than ever. Finally I can have that pimped out gun with 3 attachments (though I would have wanted 5... oh well)!
Maps are a lot more fun than MW3, and you can actually snipe now, yay! They do feel a little samey unfortunately, but the layout is good and the scenery is varied.
Weapons are great too, fun to use and each one feels significantly different from the other, something the original Black Ops lacked. I can't say that much for the balancing yet as I have yet to try them all out, but I haven't found anything horrible broken yet at least. Same goes with Scorestreaks.
Black Ops II uses dedicated servers as well, though no server browser which is a bit of a shame. But at least the issues with lag compensation and host advantage are gone, giving all players a fair chance. It remains to see if it will be infested with hackers though...
All in all, Black Ops II have reinstated some faith in the series for me, and I will be spending a lot of time with it for sure. If you are a fan of the series and haven't gotten bored with the concept yet, I suggest you buy it. If you just find CoD stale, move along to other games.
(Btw, you CAN just mute the annoying teens in the voice chat (and choose not to display the text chat) if you don't want to hear squeeky voices and insults instead of complaining that the game sucks because of this, or that you would have to mute the entire game to get rid if them. Just saying.)