burp
The bosses spawn to most missions, like Scorch spawns, or mad mike, bloodwing (although it isnt bloodwing), the bunker, but certain missions rewards give great weapons. Like the Mordecai sniper rifle that ignores shields if you get a headshot, or the lady fist pistol that has +400% critical hit damage. You can't get the rewards again.
My progression was CoD 4--1.26 K/D, WaW--1.79 K/D, MW2--1.89 K/D, Blops 1--2.32 K/D, and then Bf3 2.47 K/D
In MW2 I could just take over the game. Especially on certain maps. Like if Wasteland, Afghan, Quarry, or the one with the bridge and all rainy, Underpass? or something. I would be like, gg I'm going to nuke this shit.
In WaW I almost exclusively played Sabotage, I loved that shit. My K/D of sabotage was like 2.50 and then all other playlists brought it way down.
But yeah I know what you mean with the 3 friends. I literally play with like 3 people now as well. Ever since I abandoned the CoD series, I don't play with 90% of my friends list.