[Lord_Destros]

Personally:

CS 1.6 > CS:S (dislike recoil and much of the gameplay in general)
HL2 = HL (For some reason HL2 make me want to finish as HL did. Score is biased since I only went through part of HL2).
DoD:S > DoD (yeah I know alot of people here like DoD more but mehh).
Haven't tried TF2 yet, so I can't compare it to TFC, but it looks 1337.