You know, it's really hard to pinpoint for me what made COD4 so amazing. I say it's one of my favorite games all the time, but I really can't describe it that well when I get asked why. I'll give it a shot now, but don't expect anything great. I apologize in advance for the big paragraphs coming up.
Let's start with the campaign. Holy shit what an amazing thrill ride. I mean seriously, for a military shooter of all things, the campaign was so full and satisfying. One second you're in the heat of battle, the next you're sneaking around in a ghillie suit, and it all flows seamlessly. Not like MW2 or Black Ops where it can't calm the hell down and I certainly couldn't immerse myself in it. It's pretty much just like Yahtzee said in his MW2 review; it's like they couldn't believe how well the formula for COD4 worked, so they tried replicating it over and over again in the sequel, and just ended up over saturating it. All that, plus the ending was just immensely satisfying for me. I mean, I walked away from my xbox just feeling good on the inside with how well the story wrapped up. Even today I still remember how I felt at that moment about 3 years ago.
Now on to what made COD4 almost exclusively the only game I played for around a year after it's release; the multiplayer. I'm not quite sure what had me coming back day after day to the multiplayer, but it probably had something to do with the experience system. It was fun getting points for kills and planting/defusing the bomb and unlocking weapons and finding out what works best for you. (Red dot AK-47 for Deathmatch, silenced P90 for S&D) For me, it was a small circle of friends and we got in a party almost every night and just played the hell outta every mode for hours on end, and that went on for at leased a year straight; we just couldn't get enough. I still go back once in a while for a couple of sabotage games just for fun.
All in all, it was a perfectly rounded game with a roller coaster ride campaign and addicting as hell multiplayer that left an impression on my gaming life that's gonna stay with me forever.
Again, sorry for the long paragraphs, but I figured if there was a time for me to discuss in detail why I love COD4 so much, this is the topic to do it in.