I would have to say modern. Red Orchestra 2, Team Fortress 2, Battlefield 3, Crysis 1, Half-Life 2 + the episodes are some of my favorites.
gMcR's forum posts
MGS4 > MGS > MGS2 > MGS3 > PW
I haven't played ground zeroes yet, and I'm not really hyped for it. The series should have ended with the 4th installment.
The combat and animations need a lot more work but otherwise looks decent.
I agree. I doubt it will improve much though.