Super Mario Bros. Crossover
For an indie title of dubious legality (pft, what fair use?), Super Mario Bros. Crossover hits a spot that we'd all but forgotten about. What kid with a SNES and an N64 didn't fantasize about Link, Samus, Mega Man and more helping Mario to take over the Mushroom Kingdom and annihilate Bowser with ice beams and hookshots?
It was the stuff of dreams, and Nintendo was never going to make it happen. There's a perverse joy to playing Crossover (or its outstanding sequel) and rolling over the original Super Mario Bros. levels as a babe in a power suit with powers far surpassing Mario's. It does take most of the challenge out of the game, but that's hardly the point of this particular fantasy-turned-reality.