1: Best unlockable system ever. So fun going for challenges and camos. Honestly never got good at every gun on COD until this one. Most creative and fun unlockable system yet.
2: Guns come in every shape, size, and capability possible. I mean they freakin got a 3 round burst SMG. The LMGs are more different than ever before. QQB and HAMR are basically cousins of assault rifles. The shotguns are more different than ever before. An four round burst, slug shot, pump action, and basically semi automatic(can be automatic with quick spamming). Every type imaginable. A hard hitting 3 round burst assault riffles, and fast 3 round burst assault rifle. 2 semi automatics that have two different purposes. Snipers range from super fast and weak, to super slow and 1 shot kills. Now we have the peacekeaper!?!? OMG it don't get any better. The pistils have 3 round bust, automatic, SHOTGUN, and semi automatic. The only thing we are missing is the python. Which treyarc, a magnum type weapon should be put in as next DLC weapon. Then this game would have every type weapon imaginable.
EDIT: a launcher like in MW3 wouldn't be bad either. Like the warmachine but weaker.
3: Gamemodes have never been more diverse. Multiteam, groundwar, free for all, and regular are the size teams we can have. With these teams we can play kill confirm(scorestreak heaven), capture the flag, King of the freakin hill(hardpoint), regular deathmatch, Search and destroy(should be a party game because of the fun!), domination, demolition(search and destroy the non party game version), headquarter( search and destroy/ hardpoint/ domination). The party games have everything besides infection. Treyarc that would be the gamemode to add.
4: The maps are from small to medium size, but are the beastiest small medium sized maps I've seen in COD yet. Treyarc just had more color and more creativity when it comes to map design and color. Spawns are a little crazy, but I put it this way, your spawning on them also. Which give you the surprise. If you get spawn on top of, then you should be watching your back.
5: good create a class options, just needs a wildcard that allows us to totally skip a perk tier and put three in an other one. But each perk teir has great ones inside of it, and wont be overlooked and unused at one point in gamestyle changes. Would like to see flamethrower attachment again though. I mean you get kill along with them, so not that OP unless you spraying and running.
The lag and hitmarker problems I only hear about, isn't a problem for me. I bet a lot of people have no problem with lag or hitmarker detection. I bet it's console issues( cough cough...PS3), and bad aiming.