interesting question, I think that it would be doable. Of course, the sophistication of the graphics and music is not doable to any extent (unless you get a team of pros sometime soon). The system itself is not too tough I don't think, there are relatively few things going on. the difficulty would be dealing with the artificial intelligence of the enemies (or not if you just had player vs player only). you could represent the terrain of different heights easily enough (maybe even use various z levels)