Least cod4 you could get max rank after a few good weeks of playing. That or use a rank editor.
But CoD4 became even more fun for me with all the unlocks. I can't say the same with other recent games. It was more like unlock everything and I never played it again. If there was an option that allowed anyone to access all the unlocks regardless of their rank for unranked servers I'd never play on ranked servers (If the core gameplay was fun). Maybe if they added a $5 or $10 option to unlock everything. I'd go for that.
I've honestly had enough, limited unlocks was livable but now it's just plain stupid. Way things are going this is what you get when you start playing and the rest will be unlocks