I loved the Double Dragon series and Battletoads, but I didn't really think they counted as Fighting Games. Battletoads, though, had some unique gameplay with the brawler stages, the vehicle stages, and the frickin' stage with all the snakes. I am not sure if I ever beat that stage. I think I had to use the ole Game Genie to get to the end. And the villainess had a balcony you could do Shakespeare from.
I believe I always used Spinal or Orchid from Killer Instict. I liked Spinal's combo finishers where he morphed into the character he was fighting.
And actually kurruption, I thought Sabrewulf was supposed to be one of the easier characters to learn. His moves were primarily charge based.