I realise it's down to what you've played and what you remember, but I think the easiest ones are 2, 3, 5, 8, 12 and 14. 16 is probably the hardest/most obscure. It's early days, but I really think 2 is unbelievably easy. Maybe I've just heard it too much.
Rhythm 2
RPG 5
Shmup 4
FPS 1
Survival Horror 1 (Not sure I agree with this category, but this is how it's generally listed)
Action/Adventure 2
Sports 2
Adventure 1
Puzzle 1
TPS 1