Half Life 2 is a textbook example of how to do an FPS right, Episode One even more so due to it’s flawless pacing between puzzles and combat. I actually rather enjoyed getting One Free Bullet- it was almost a completely different game playing it that way.
HL2+ Episodes is required reading for any self respected videogamer, much like Prince of Persia: The Sands of Time, Splinter Cell - Chaos Theory, Metal Gear Solid 3: Subsistence, Mass Effect 2, Rainbow Six Vegas, Xenogears, Burnout Revenge, etc.
I also have required reading lists for games that are merely good but can be improved on, such as Mirror’s Edge, S.T.A.L.K.E.R. Shadow of Chernobyl, Final Fantasy XIII, Red Dead Redemption, F.E.A.R., Jet Set Radio Future, Halo 3 ODST, Alan Wake, and so forth.