NMH is not for everyone.
Actually, it's not for over 90% of the video game playing audience IMO; it really is a niche IP that will hold massive appeal to those in that small group, but little to those who aren't.
So either you know NMH is your kind of thing, or you may end up finding the series to be a massive waste of time if you have different tastes.
Loved the original; played it more than any other early Wii title. Would buy the PS3 port if it were available in the States. Never finished the second, but would buy a PS3 Move port anyway.
Probably about as mainstream as a Goichi Suda game will get, but if you don't know who 51 is, much less even care, that doesn't hold much weight.







