If playing Contra III on the Virtual Console is too inauthentic an experience for you, then these versions of Contra would no doubt make you backflip to death. Youtube user iniche has compiled videos of Contra variants, from the official (Ocean Software's ports of Gryzor, a.k.a. Contra, for various underpowered European computers, like the Spectrum 128 version seen here) to the spectacularly unofficial (a Famicom remake of Contra III).
Especially notable is a (sort of) original fake Contra game called Super Contra 8. That's, like, four more Contra than the last official Konami Contra game -- and it's super.