This Thursday I'm doing a presentation at my university on a brief history of video game music- when I'm done talking about the history of the genre and how some artists use influences from the style today (Dragon Force, Anamanaguchi, The Postal Service [a little bit], etc), I get to play my own music which is all video game-ish...
I'm also considering playing some video game music that's considered some of the best written. Already I'm planning on playing (on piano, which will be provided) the Mario Bros. 1 theme, and maybe the Pac Man theme.

What other pieces do you think would really appeal to my audience (a bunch of science majors [nerds] who'll probably be completely captivated by my presentation) ?

One word...METROID!!!!!!!!!!!!!!!!!!!!

Noted, but as it turns out I had to hurry through most of my presentation 'cause they were timing it really rigorously (for whatever reason. I think there was some kind of competition going on between oral presentations, so they had to judge them evenly. I was just there for fun, honestly. How often do you get to talk about something you enjoy [video game music] at an event full of nerds?), so I didn't really have a chance to elaborate on much music other than my own, which took up a fair amount of time.
This comment has been way too long.

Although, I did mention Metroid (by Hirokazu Tanaka, who also did Kid Icarus).