You have access to the same stuff everyone else has access to
Oh sure, after spending hours and hours of my life. In addition, due to the way things work out, there WILL be better weapons/perks/whatever. In addition, there will be builds that are counters to mine, like a sniper taking out shotgun users on a more open map. Now, it is within reason that players should adapt to that, but when you play a certain class heavily, and all you have are unlocks for that class, switching out on different maps that do not support your chosen play style becomes difficult, sometimes downright unbearable.
There is no dispute that Quake has a more even playing field, because you literally do not have to make a choice. Everybody spawns with the same weapon, has access to the same weapons, and to the same powerups the INSTANT they join the map, regardless of play time. A noob can pick up the BFG same as a pro. Not so in Call of Duty, where a noob is stuck with the crappy starting weapon while a long time player gets access to the M-16 with all their doodads, powerups, perks, and other cheap tricks (did they really need to add an exploding remote control car to the game?), not to mention kill streaks.
I played Modern Warfare and Modern Warfare 2 a lot. I mean a ton. And what I came out on the other side realizing was that much of the gameplay of those games was simply finding out the way to be the cheesiest, cheapest bastard on the map. Finding the cheapest, easiest spot to camp/roam around in, get the best weapon for that specific spot, and most players wouldn't even be able to see you before they died. No skill involved. I spent most of my time reloading my weapon than actually fighting. Now, that isn't to say that skill didn't come into play many times, because it died, but I found many, many games could be won by finding out the cheesiest spot to hide, and then sit there and rake in the kills with uber one-shot weapons like the M-16 with headshots.
Or god forbid, akimbo 1887s.