I too encountered
Battletoads as an infernally difficult NES game, and never would have seen the end of it had not emulators come along, so you can save your progress every two seconds during that speeder bikes stage. Not to mention the hypno-orb.
What kept me coming back was the cartoon-exaggeration, which I hadn't seen in a video game before. Punch a baddie, and this Volkswagen-sized fist appears briefly on the screen. Stomp someone, and see the underside of a colossal boot.
Did anyone else think, upon first seeing this game, that it was a transparent TMNT rip-off? I mean, look at the character design.