If I had to rank them, I guess it'd go like;
2. Halo CE
3. Halo 2
4. COD World at War
5. COD Modern Warfare
Possibly unpopular opinion; as great as the 2000s were, I actually think the 2010s might end up being better in terms of FPS games by the time they end at the close of this year, once Doom Eternal is out.
YEAH!! *revs chainsaw for monster killing fun time*
Some days I just blow up.