COD4 maps > MW2 maps.
At least everyone I know who was a hardcore COD4 player was disappointed (initially) with MW2. In the end, it's a better game than MW3, but Ghosts is better than MW2 in terms of game structure, although the maps still aren't exceptionally great. You can't ever cover your back 100%, too many ways to get to you and places for people to spawn. In COD4 I loved certain maps and looked forward to them. I never did that in MW3 and not really in Ghosts either. I guess they do have some good sniper maps in this one. I like playing on Whiteout and Stonehaven just for sniper battles. Actually I find the snipers with thermal are pretty overpowered if you are good with them. I use Overkill with Honey Badger and VKS thermal and I have a 3.80 right now.
My accuracy is 38% because I snipe on pretty much every map and that's the highest it's been in any COD so far.
The main issue I have is the 'intentional death respawn system'. It's the worst yet in this game. You die once and a lot of times it = 3 deaths. 1 legitimate death, then 2 respawns right in front of the hallway some camper has been aiming down for the last 3 minutes - or you come back at the top of a stairwell where some guy just spawned right below it and he shoots you in the back after you take 3 steps. And I know they didn't 'mess up' when making the spawns, they did that intentionally so that the complete beginners could have a chance to get a kill in multiplayer, or to generally try to make things as 1:1 as possible. I understand their reasoning but they need to come up with a better way of making it more balanced. I don't think it needs to be drastically different, they just need to make the ranking system easier so that people who get few kills can still advance. Actually, the Squad Points idea is brilliant for that.
I like all the customization and perks etc. to a degree but it's overkill, and that all started with MW2. COD4 rewarded you the most for aiming skill, map knowledge, and reflexes (despite 3 grenades perk and martyrdom). The second they added stuff like heartbeat sensor, final stand, and even thermal, the game started going downhill. As much as I used One Man Army, it was a way overpowered perk. You basically have infinite claymores, etc. Dead Man's Hand? Give me a break. I'm so glad the death streak garbage is not in this version, and I think that's a lot of why I like it better than MW3. The kill streaks are not too overpowered either, but definitely there is more camping in this version that I've seen in a while.
Anyway, I've been playing Modern Warfare for a long time so I'm pretty opinionated I guess you could say.
Feel free to disagree. I'm just like that and I just do things my own way.
I literally took Black Ops back after two hours of playing it and put it toward repurchasing COD4. Didn't touch Black Ops 2 either. I'm just like that. I literally never ever used Final Stand in any COD either because I simply hate the idea of people being rewarded for being bad at the game. Only death streak I ever used was Revenge and Pain Killer.