Just made all retroachievemens in this game in hardcode mode (without save states). Probably the easiest NES game with the easiest achievement set.
If you have never played, I recommend giving it a try. The gameplay is great, nice soundtrack.
What is the easiest game for NES in your opinion?
Plenty of cheaper options. The Kishi is great for smaller phones and X2 is almost as nice and even cheaper. They're perfect for emulators but suck for shooters.