This is a hard one indeed, I'll give you these as definite candidates in no particular order.
1. Rust (mw2)
2. Shipment (cod4)
3. Highrise (mw2)
4. Terminal (mw3, I like the look of it more than mw2's)
5. Nuketown 2025 (BO2, prefer it over original nuketown and 2065)
6. Standoff (BO2)
7. Dome (MW3)
8. Hardhat (MW3)
9. Detroit (AW) (SAY WUT!)
Didn't include BO1 or Ghost maps as I didn't really like those games, stuck with mw for the year of BO1 and BO2 for the year of Ghost.
Started during late MW2/early BO1.
Here ya go, my top 10:
1. Strikezone from Ghosts
2. Studio / Firing Range from BO2 / BO1
3. Evac from BO3
4. Favela from MW2/Ghosts
5. Pipeline / Atlas Gorge from COD4/AW
6. Quarry from MW2
7. Erosion from MW3 (free goodies are the best, I wanna see more, none of this preorder or eventually get it free BS)
8. Prison Break or Stormfront from Ghosts (shocker, a tie.)
9. Sideshow from AW
10. Standoff from BO2
2. Terminal (from MW2 and MW3, preferably from MW2)
3. Nuketown(BO1 and BO2 only)
6. High Rise(MW2)
7. Wasteland, Afghan, and Firing Range (Studio) This is a 3-way tie cause this is a hard one.