Really? What rank are you at now? It didn't take me that long to get a pretty high rank, but then again I played for at least a few hours each day.
Contra 3 on GBA is the hardest side-scrolling game I've ever played. It's basically a harder Alien Wars. No smart bombs, no continues, and the overhead levels were replaced with some Contra: Hard Corps levels. It's truly the hardest Contra yet. No ifs, ands, or buts. I even found the very first game easier.
Mega Man & Bass is really flipping difficult too. I mean, Capcom made both characters cripples. Mega Man can shoot real well but jumps like an elephant on a planet with 3x gravity (bad for platforming, and some platforms are nigh-impossible without a good jump) and Bass has to stand still to shoot and can't charge his buster (bad for those bosses that like to run and jump around for the whole battle). Took me years to beat the Super Famicom version. I can make the game my, er, "female dog" now though.