I voted Treyarch because in this series (which I think is the definition of mediocrity by the way because I may sound a bit fanboyish here) Treyarch is the only one still trying, and they always have tried.
Infinity Ward stopped caring about making a good experience and focused entirely on the multiplayer with MW2, and this was before they all got fired and made MW3. Their games are stale to me, I wish they wouldn't be, but there you go.
Infinity Ward:
CoD 1: Ok I guess, hasn't aged well.
CoD 2: Better, but hasn't aged well.
CoD 4: Really loved, has aged well and has been the template for the 'modern' CoDs, and it's campaign is still enjoyable.
MW2: I really, really hated MW2. It's my least favourite Call of Duty overall.
MW3: An upgrade to MW2 (although nobody will agree with me), but it's still awful, and Modern Warfare 3 has the worst spawns in gaming history, even post patch. It's campaign is god awful as well, CoD's gameplay cannot support the lack of atmosphere, good storyline or interesting characters.
Treyarch:
CoD 2: BRO (heh, heh, bro): I actually quite liked it, it hasn't aged well but it's focus on characters is enjoyable.
CoD 3: Same as BRO, just not as good as it, introduced one of my favourite game modes in games (War).
CoD WaW: It's a carbon copy of CoD 4 but it's removed all the nonsense of it and tried upgrading it. WaW's my favourite Call of Duty.
CoD Black Ops: It tried being original (for Call of Duty standards anyway) and creative with it's ideas, it's campaign is certainly proof of that with it's interesting twists and attempts at character development.
CoD Black Ops II: Same as Black Ops, and I'd actually rate it's campaign as best in series despite it's horrific gameplay because it's restricted by Call of Duty standards. Multiplayer is meh but it's tried changing some things.
Infinity Ward stopped caring about making a good experience and focused entirely on the multiplayer with MW2, and this was before they all got fired and made MW3. Their games are stale to me, I wish they wouldn't be, but there you go.
Infinity Ward:
CoD 1: Ok I guess, hasn't aged well.
CoD 2: Better, but hasn't aged well.
CoD 4: Really loved, has aged well and has been the template for the 'modern' CoDs, and it's campaign is still enjoyable.
MW2: I really, really hated MW2. It's my least favourite Call of Duty overall.
MW3: An upgrade to MW2 (although nobody will agree with me), but it's still awful, and Modern Warfare 3 has the worst spawns in gaming history, even post patch. It's campaign is god awful as well, CoD's gameplay cannot support the lack of atmosphere, good storyline or interesting characters.
Treyarch:
CoD 2: BRO (heh, heh, bro): I actually quite liked it, it hasn't aged well but it's focus on characters is enjoyable.
CoD 3: Same as BRO, just not as good as it, introduced one of my favourite game modes in games (War).
CoD WaW: It's a carbon copy of CoD 4 but it's removed all the nonsense of it and tried upgrading it. WaW's my favourite Call of Duty.
CoD Black Ops: It tried being original (for Call of Duty standards anyway) and creative with it's ideas, it's campaign is certainly proof of that with it's interesting twists and attempts at character development.
CoD Black Ops II: Same as Black Ops, and I'd actually rate it's campaign as best in series despite it's horrific gameplay because it's restricted by Call of Duty standards. Multiplayer is meh but it's tried changing some things.