Kart Fighter (Famicom)
Released sometime between 1993 and 1994, this game made the logical choice of taking the characters from Mario Kart and having them fight Street Fighter style. Most of the characters play the same and the move list is severely limited, but it still manages to be fun. The developer, Hummer Team, was notorious for reusing engines and assets, and thus elements of this game show up in other games.
Hong Kong 97 (Super Famicom)
This bootleg isn't a rip-off or port of another game, it's just an unauthorized release. It's mostly original (images are ripped from all over the place, though mostly in the form of .jpeg files) and a simple shoot-em-up. The plot involves a relative of Bruce Lee going into Hong Kong to karate Chinese communist soldiers to death. That sounds tame, but the craziness is difficult to describe, from the graphic game over screen to the absurd difficulty of the game itself (one hit ends the game instantly).
Super Smash Land (PC)
SSL is a fan game, taking it outside the realms of bootleg for some. Still, it's an attempt at porting the original Super Smash Bros. to the GameBoy, albeit with a different roster. Though it runs on PC and Mac it sticks to the GameBoy motif, from the visuals and sounds to the controls, relying on just the arrow, Z, and X keys.
World Heroes 2 (Famicom)
Predating the crossover fighting game by a few years, World Heroes 2 is a hodgepodge of intellectual properties fighting for dominance in the world of copyright infringement. The bulk of the roster is pulled from Street Fighter and Fatal Fury, but there's a few holdouts including Super Mario, Leonardo from TMNT, Goku, and Final Fight's Haggar. In a weird point of consistency the music selection is pulled from the same games as the characters.
Dragon Fighter (Famicom)
The major difference between Dragon Fighter and World Heroes 2 is that Dragon Fighter pulls its characters from Sega Genesis fighting games, many of them coming from the Mortal Kombat franchise and Justice League: Task Force. It's much more difficult than World Heroes 2, largely because of an overly defensive AI, but edges out its sort-of counterpart by having a wider range of moves. That said, both suffer from programming bugs, though Dragon Fighter's are more on the audio-visual end of things.
Pokemon Diamond and Jade (GameBoy Color)
This is perhaps the most devastatingly lazy bootleg on the list. It's a butchered version of the first generation of Telefang games, games which are themselves in the style of Pokemon in the first place. But the attempt to actually pass these off as Pokemon games ends with the box art and shoddy title screen. Somehow during the translation process the pirates managed to butcher the game in such a way that it can become nearly unplayable, and several of the original's unique functions will not only do nothing in game, but they'll actually crash the game. The translation itself is a thing of beauty and worth checking out on its own, but if you're looking to actually get through this game prepare for lots of frustration. Depending on how you play it, it won't even load save files.