Here’s an attempt at an answer key:
1: Contra (NES)
2: ?
3: Super Mario Bros (NES)
4: Donkey Kong (Arcade)
5: Duck Hunt (NES)
6: Pacman (Arcade)
7: Berzerk (Arcade) note that this one also has a little bit of Donkey Kong at the beginning of the sound. This is apparently a mistake.
8: Pitfall (Atari 2600)
9: Galaga (Arcade)
10: Joust (Arcade)
11: Gorf (Arcade)
12: Defender (Arcade)
13: ?
14: ?
15: Q*Bert (Arcade)
16: Pacman (Atari 2600)
17: Gauntlet (Arcade)
18: Combat (Atari 2600)
19: Burger Time (Arcade)
20: Pacman (Arcade)
21: ?
22: Definitely not Final Fight
23: ET (Atari 2600)
24: Frogger (Arcade)