Like Black_Tiger, I have a soft spot in my heart for SideArms.
EVEN BACK IN THE DAY, when it was first available for TG-16, it was an old-skool shoot-em-up. It did not scream "new, fresh, aesthetically groundbreaking" like the newer (and soon-to-be released) cousins...
HOWEVER, despite seeming somewhat dated (mechanics and aesthetics), it is a solid game. Sure, the game recycles some bosses (mini-bosses), and the power-up system is a variation of Capcom's own 1941 games (not everyone will get warm-up to this power-up system...but if you've played 1941 & kin then you will be fine).
I simply love flipping back and forth, flying frantically around the screen, and taking out enemies ALL AROUND YOU. Some segments are wonderfully cruel and painful until you've figured out a winning strategy.It has horizontally- as well as vertically-scrolling segments, which is nice to break up the monotony. Also, there are segments where your main objective is simply to DODGE the oncoming (big-ass) missiles. I personally like the variety of elements and the pacing of the game.
I found the game to be a nice challenge (you keep going back to get a little further).
I still have to sink my teeth into the special CD version ("Before Christ")...I played through it many, many years ago (1999? 2000?), and it is certainly a nice treat for folks who enjoyed the game. The Red Book closely follows the chiptunes (the chiptunes are superior, I think, but I love listening to the Red Book for variety...it's nice to have more...also, the chiptunes emphasize the melody...whereas the Red Book has an interesting layering of instruments, subduing the melody so it isn't blaring "IN YO' FACE"...)
Spriggan Mk 2, as BonkBonknutsTomatenuts stated, is certainly nothing like Spriggan. I was disappointed at first...but the game has certainly grown on me. I still haven't beaten it (I'm only 3? 4? levels in), but it is on my list of games to get back to.
The presentation in Mk 2 is certainly nice, precise and polished. Unusual for the genre, there is a pretty elaborate story (not that I understand it)...but I'm not sure the story really adds anything (it might, it really depends on how well it is written...even though Bloody Wolf has a generic storyline, the "plot twist" towards the end of the game added a nice touch (IMHO)...if Spriggan Mk 2's story has anything approaching this, then I would definitely list it as a "plus".
It's been many years since I've played Mk 2, so I should pull it out and play it alongside CD Before Christ SideArms.