This is a tough one to organise, so the order is subject to change. I can get it roughly in the correct order though:
1. Half Life 2
2. Command & Conquer
3. Borderlands 2 (and 1, but I had to pick)
4. Command & Conquer: Red Alert 2 ( - Yuri's Revenge)
5. Legend of Zelda: Ocarina Of Time (I've played it to death, so it's not number 1)
6. Minecraft
7. Starcraft (I suck at it so hard, but it's so much fun)
8. Warhammer 40k: Dawn Of War
9. Warhammer 40k: Space Marine
10. Oddword: Abe's Oddysee
11. Goldeneye64
12. Timesplitters 2 (It brought back all the feels from Goldeneye)
13. Command & Conquer: Tiberian Sun (actually mostly for the amazing OST)
14. Legend of Zelda: The Wind Waker
15. Legend of Zelda: The Minish Cap
16. Half Life (+ expansion packs)
17. The Binding Of Isaac (if you've not played it, go play it)
18. Dungeon Keeper
19. Rollercoaster Tycoon 2 (how did I nearly forget?!)
20. Sam & Max Hit The Road (RIP Lucasarts)
1. Half Life 2
2. Command & Conquer
3. Borderlands 2 (and 1, but I had to pick)
4. Command & Conquer: Red Alert 2 ( - Yuri's Revenge)
5. Legend of Zelda: Ocarina Of Time (I've played it to death, so it's not number 1)
6. Minecraft
7. Starcraft (I suck at it so hard, but it's so much fun)
8. Warhammer 40k: Dawn Of War
9. Warhammer 40k: Space Marine
10. Oddword: Abe's Oddysee
11. Goldeneye64
12. Timesplitters 2 (It brought back all the feels from Goldeneye)
13. Command & Conquer: Tiberian Sun (actually mostly for the amazing OST)
14. Legend of Zelda: The Wind Waker
15. Legend of Zelda: The Minish Cap
16. Half Life (+ expansion packs)
17. The Binding Of Isaac (if you've not played it, go play it)
18. Dungeon Keeper
19. Rollercoaster Tycoon 2 (how did I nearly forget?!)
20. Sam & Max Hit The Road (RIP Lucasarts)