According to the good folks at Ithaca Audio, "Space Invaders," released in 1978, was the first video game to include a continuous soundtrack. Since that time, there's been a few more that have been drilled into our collective video game brain.
This mashup, called Game Theory, charts the evolution in video game tracks from Atari, to Game Boy, to SNES, to N64 and PS1 gems, right up to today's current epics. The visual accompanyments are also a great touch, and will give you a pretty thorough flashback to those nights in 5th grade, where a wild Friday night was staying up past bedtime to "beat the boss" of that really difficult level.
[H/T: The Atlantic]