1. Red Orchestra
2. Fallout 2
3. Scortched Earth
4. Resident Evil 4
5. Warcraft 3
Because...
1. The most realistic shooter ever made, which is probably why it didn't sell as well as Call-of-Attention-Deficit-Disorder. You moved at the speeds of a normal human (1-2mph walk 6-8mph sprint) and even had suttle realisms like when you press forward it takes a second to work up to full speed (like taking the first step in real life). Realistic reload speeds and recoil also real ballistics including bullet drop and time of flight, also realism in health no taking several rounds. Even barrel-wear and overheating of some weapons.
2. Possibly the most overlooked game of all time, even watching someone else play Fallout 2 is like watching an amazing movie. There was so much to do and see there was a huge world with countless side-things.
3. Old PC game played like Worms Armegedon In fact worms copied Scorched earth for the most part. Calculate mathematically your tanks firing, angle, positions, weapons ect amazing multiplayer fun.
4. Scared the *&^( out of me, really forces you to feel submerged.
5. The custom map/game editor was the best of its time, there were so many amazing custom user-made games that I never really played the actual game itself lol.