R-Type II by Irem, arcade release in 1989.
"But wait, Retro Game of the Day, didn't you already cover this game before?" Yes.. and no. Super R-Type did release for the SNES a couple of years later, that much is true, but this game is different from that version ("II" is the original, whereas "Super" is a remix of sorts).
That being the case, it would take a clueless person to overlook the fact that this was the first (ahem) sequel to the phenomenal shooter R-Type, released a couple of years prior to this version. II wasn't a huge advancement over the first one, more of a refinement than anything - but it did have new levels, and a couple of new weapons to play with.
Like most folks who played thru Super, there might not seem much reason to revisit the arcade original, but some completionists might argue otherwise. Different bosses, different music, altered levels (and level designs), a smoother playing experience (the SNES version is well known for having heavy slowdown) are all good arguments that R-Type II might deserve your attention.
Still, there's a few bones to pick with the game. Whereas the first one was more epic, and certainly fresher and more original at the time, in some ways this sequel seems a bit lazy and conservative... bland even. It looks good, with lots of detail (as Irem games usually were) but the background scenery wasn't quite as enthralling at it's predecessor, and the level themes seemed a bit less inspired this time around.
Nitpicking aside, there's some good blasting to be found in this somewhat-overlooked R-Type. It may not measure up to some of its brothers, but it's still a very solid episode in one of the true classic series of gaming.