4 - Dr. Mario (NES, Game Boy)
Already an unlicensed plumber, Mario apparently thought it was also cool to impersonate a practicing physician. Lucky for us his foray into prescription drugs resulted in one of the most addicting puzzle games of the era. Created in a time when Tetris was the end-all be-all of floaty block games (even more than it is now), Dr. Mario gave us an actual reason to clear the screen - the elimination of multicolored viruses. So, rather than just clearing lines for the sake of clearing lines, you had a visible goal on every level. After matching four pills with a like-colored virus, the remaining colored piece would fall until it hit another piece. This tiny bit of strategy made all the difference at a time when we could have just played a packed-in copy of Tetris.
Versus modes let you toss leftover blocks on the opponents' side, making it a more intense experience when compared to plain ol' Tetris. The addicting gameplay translated perfectly onto the first Game Boy as well, making it one of the first Nintendo games you'd be just as likely to see a grandma playing as you would a hardcore Mario freak.
We'd feel a little silly if we didn't give a shout out to the music, which contains some of the most memorable NES tunes ever. Enjoy...