FS(GBA) is an extension of MC, because the sprites are very similar. And both have to do with the Four Sword. And both are the most recent sprite style of the zeries.
ALttP is nostalgic, yes, but there are indeed obvious problems with it. Take the colors, for instance. It's all very washed-down in terms of colors, not like thevibrant and bright MC sprites.
The Oracle games (and LA) are okay, but their lower resolutions make fangames on them... well, different. The trick with a good fangame is that the sprites must conform to the quality of the lowest-quality sprite in the game. LA/OoS/OoA kept the resolution and the colors to a good minimum on the sprites, and Link's oh-so-hilariously-reusable poses only accentuate how simplistic the style is.
I vote MC, because it's apparently "in".