I used to have ENTER THE NINJA on VHS back in the 80's. Enjoyed it back in the day. Don't know what I would think of it now, though!
Saw a few of the Godfrey Ho flicks around the same time...and can't honestly say that I would want to revisit any of those on purpose. ha ha!
I do have a few favorites among the more serious Japanese Ninja films, though, like:
WARRIOR OF THE WIND (Kaze no Bushi) -- 1964
BAND OF ASSASSINS (Shinobi no Mono) -- film series, starting in 1962
NINJA HUNT (Ninja Gai) --1964 (not the more recent one)
CASTLE OF OWLS (Ninja Hicho Fukuro no Shiro) --1963
But, I have to admit I used to get a big kick out of the trashy Sho Kosugi and Godfrey Ho flicks once upon a time!
REVENGE OF THE NINJA was my favorite Kosugi vehicle.