Got tired of waiting on ACA Guevara and picked up SNK 40th (PS4) - wish I'd done so earlier, it's a lovely bit of work. As always with modern releases of vintage 2D action, my primary concern was input lag. Everything seems more than sufficiently tight, with the stuff I already have on ACA (Ikari, Dogosoken, TANK, Psycho Soldier and Alpha Mission) handling just like I'm used to.
Wanna take a crack at the TRUE AND HONEST Ikari III before my Ikari and Dogo no-misses fade too far into the rear-view.

Jesus Balls it's tough, yet keenly tactical, just like its predecessors. Had to laugh at the utterly alien courtesy of tank exit i-frames, an absolute luxury coming in from Ikari's unflinching meanness. Arigato, Obada-san! :3
Search And Rescue, the other game I bought this for, is beautiful

Zombies with guns, that ain't good. Zombies in Power Loaders, oh hell naw. Hey WTF, stop all the mutating! The way
Totally Not Xenomorphs' iconic black silhouettes rise from ruined hosts is so badass.

JUST A MAN / AND HE WILL 2 SURWIWE ♫ 

Don't touch me you
SPACE FUCKS
How could this happen to me?!
At a glance it seems a bit easier than the Ikaris, with quick movement, a long and lightning-quick dodge roll, and surprisingly generous charge shots. OTOH, the enemies don't play around, and like any good dodge roll, this one's generosity is double-edged. Looking forward to seeing this through. Ultra-cool take on the
Aliens aesthetic, in any case... seamlessly translates an atmosphere of corruption and doom to one man army R2RKMF context. I love all the
BR00TAL corrupted machines, too!
ROBO-DREAMS CAN COME TRUE / THIS COULD HAPPEN TO YOU ♫ 
Mortificator wrote:
I have to give these space dudes credit, they search every inch of the ship for survivors... most people would've taken one look at the infested animated corpses and floors covered in flesh and run screaming for an orbital strike.
^^^ WORD 
I really like ADK's Battle Field/Time Soldiers, too. It plays like an Ikari minus that trilogy's trademark death-march plod. Much twitch-friendlier, on first impressions. Best death scream ever, holy shit it's ridiculous.

The 16way aim is an interesting choice... felt a little distracting at first, but I'm finding its subtlety a godsend in tight spots where 8way would require a strafe to connect.
Unfortunately I think SAR might be bugged - it seems to use "single stick" (look where you're moving) controls at all times, despite my setting it to dual.
Frank Cifaldi mentioned Ikari III doing this for usability reasons, but I can't see any reason for it here - if anything it cramps the cool dive n' shoot mechanic. It's not the end of the world - you can still strafe by keeping the right stick trained on the desired direction - but it'd be nice to have it play as solidly as Guevara. Have reached out to see what's up.
I have to say, head-to-head, I slightly prefer Hamster's LS-30 setup. Besides the right stick's snap aim, they also let you set any button as [turn left] or [turn right], with optional variable-speed autofire. This is a godsend when you need deadly-precise adjustments - I always set Square/X to [Left/Right], with Triangle/Circle the same plus autofire. The latter's very handy in Dogo, when you wanna lash the sword back and forth while advancing, for maximum
GAMUSHARA 

40th lets you set the buttons to turn, specifically one per cardinal direction, but it's an either/or choice - doing so will disable the right stick's equivalent. Again, as with SAR's possible bug, it's nothing major, but I do appreciate ACA's extra precision (especially given the PS4's innately floppy sticks).
Regardless, even if Guevara, SAR and Time Soldiers (plus the excellently batshit rotary STG Bermuda Triangle, and its friendlier sequel World Wars, and the classy Force Pod hori
GENSHITOU) never show up on ACA, this collection has 'em in fine form. Unreservedly recommended.
EDIT: Or not. This comp unfortunately has some nasty bugs in
Search And Rescue, at the least. Caveat emptor.