Yes, the original R-Type was brilliant. And of course a sequel was more than welcome. But the sequel we got was just far too similar to the first. It feels more like an expansion pack than anything else. The first level of R-Type II is virtually the exact same as before. Even the music hasn't changed.
Level 2 did feature a cool, and very hard, underwater stage and there were a couple of new power ups for that crazy force orb. But it was all just too samey. IREM didn't put much imagination into this game at all. On its own, when not standing next to the first, R-Type II is still a great game but is no-doubt a rip-off when regarded as a sequel. With all of the pale imitations of R-Type that followed the original's release then they should have tried harder to make this something special.