So, Sega first announced this series of stereoscopic 3D ports/remakes for JP 3DS towards the end of last year, and now they've finally given us release dates for the international releases:
(eShop-only, $5.99/€4.99/£4.49 each.)3D Space Harrier, 3D Super Hang-On – 11/28/2013
3D Sonic The Hedgehog, 3D Altered Beast – 12/5/2013
3D Ecco the Dolphin™, 3D Galaxy Force II – 12/12/2013
3D Shinobi III, 3D Streets of Rage – 12/19/2013
The ports/conversions have been handled by M2, whose pedigree I'm sure you're all aware of, and the Japanese response to all of these re-releases has been very positive. There's a common set of features between all the games--save states, button configs, sound tests, etc--as well as options specific to each format; the MD games have a pretend-CRT screen mode, for example.
With that in mind, I figured I'd go over the two STGs, Galaxy Force II and Space Harrier, and explain what they've added/included for the 3D versions. (I haven't experienced either of them first-hand, mind you...)
GALAXY FORCE II (official site here)
-This version of the game is based on "Galaxy Force II NEO" from M2's Sega Ages release for PS2, which includes retouched/redrawn graphics and readjustments for widescreen, but you can unlock a more arcade-faithful version by clearing the game once (or just reaching the ending, you can even save-state if you have to).
-Includes one save-state and allows you to save one replay which can be watched in slow motion.
-You can move with the circle pad, d-pad or touch screen; there's also a full button config (including inverted movement), and you can even use the Circle Pad Pro as a makeshift accel/decel throttle.
-There are dipswitch settings for energy depletion speed, shield strength, initial starting energy and difficulty.
-There are three standard screen options (4:3/16:9/16:10--correct me if I'm wrong!) plus a virtual cab mode that adds a cabinet overlay to the screen and even simulates the movements of the original cabinet. (You can toggle between DX/Super DX cab simulation and even choose a different background overlay that depicts the environment outside of the cabinet, sheesh.)
-Sound options let you set the volume levels for music/SFX, and there's a toggle for the SFX generated by the movement of the virtual cabinet. You can also toggle the extra BGM jingle for Marc Land, if that's something that really bothers you.
SPACE HARRIER (official site here)
-This version is based on the arcade original, of course, but they've thrown in the X68000-exclusive boss "Haya-Oh", which can be accessed by clearing stage 18 without dying. Runs at 60FPS, I believe.
-Three-credit default, but defeating Haya-Oh unlocks a freeplay option. You can begin from any stage you've previously played, and it records scores for individual stages.
-Includes one save-state and allows you to save one replay which can be watched in slow motion.
-You can move with the circle pad, d-pad or touch screen; there's also an option to invert movement, and you can choose between a few different rates of autofire.
-There are dipswitch settings for difficulty, starting lives and extends, as well as a 60-second time trial/caravan mode (was this in the original? I honestly can't remember).
-There are three standard screen options (4:3/16:9/16:10--correct me if I'm wrong!) plus a virtual cab mode that adds a cabinet overlay to the screen and even simulates the movements of the original cabinet. (There seems to be a few different bounding box settings for character movement, too.)
-Sound options let you set the volume levels for music/SFX, and there's a toggle for the SFX generated by the movement of the virtual cabinet. The sound test also features an equaliser setting that lets you adjust individual sound channels.
Anyway, I figured some of you dudes might be as eager to play these re-releases as I am (GFII in particular). There's a decent number of screenshots on each page, so check 'em out and let me know if you think I've overlooked/missed anything important. Enjoy!
(mod edit - moved to off-topic, rail shooters)