As others have mentioned, the series hasn't moved on in great leaps and bounds but I personally feel the little tweaks they have done warrant five stars. I'm only about an hour into the campaign on the hard difficulty so for all those complaining about it being short, crank it up a notch, it'll draw the game out by an extra 50 - 75% playing time easily. Mind you, I'm not the world's best game player which brings me to Multiplayer.
It's pretty much more of the same but there's some great new maps in there and I love the custom load outs you can do. It really helps you tweak when you're not the world's best player.
I, like others, had concerns about the futuristic leap with the series but this has been done extremely well in my opinion.
Overall, I think it's a nice step forward, not leap, for the series and one where new players can leap into it without caring too much about the back story and existing players can enjoy something a little different.
Let's face it, it's Call Of Duty. It's never going to change that much but that won't stop us buying it.
To summise, great graphics, great voice acting, great story (so far) so I don't think you'll be disappointed.
For the record, I bought the Care Package edition and I thought it was good value for money compared to other so called "ltd" "special" editions etc I have bought in the past.