Half-Life 2, Half-Life 2 E1, and Half-Life E2 demonstrate the true potential of a FPS.
This game has well improved graphics, phenomenal voice acting, sweet weapons, cool enemies, and the new gravity gun (which allows you to pick up certain objects and either place them or throw them). To be honest, HL2 allow you to obliterate every single opposition even more than before.
Portal: You shall pass through unique testchambers in this game, creating and utilizing portals to get through each testchamber.
Like Half-Life, Portal has terrific voice acting, along with similar gameplay. If you are not simple-minded and love puzzle games, well actually, YOU DON'T HAVE TO BE A FAN OF PUZZLE GAMES, THIS GAME WILL KEEP YOU GLUED TO YOUR TV UNTIL THE GAME ENDS. The only flaw is that the game is a bit to short, but then again, it has no reason to be long, so that isn't necessarily a bad thing.
Team Fortress 2: Who is your king of this multiplayer game. The heavy, the scout, the soldier, the sniper, the spy, the pyro, the demoman, the engineer, OR the medic. Well, they all are great characters who have something great about them.
I have played FPSs like Resistance and Call of Duty online, but I never thought I would play such a FANTASTIC FPS like this. It combines humor with brutality and good characters with good weapons. In this game, they take pieces if a great game, and peice them together perfectly. The only flaw is NO storyline, but then again, it being a only a online based, it doesn't exactly need one.
OVERALL: Very minor flaws
Great gameplay
Great graphics
Great voice acting
Equal up to the perfect game pack.