While the game performs faithfully to the arcade original with accurate emulation, the game name is still misleading as the visuals are more or less the same with the player ship being updated and the edges no longer looking jaggy in HD Mode so it's basically G-Darius in upscaled high-res glory. The Steam version of G-Darius HD has on more game mode exclusive to it, G-Darius Exhibition, which is an experimental game mode offering ultrawide gameplay experience with the HUD and in-game UI re-positioned. That game mode puts Playstation emulators with widescreen feature to shame with more accurate emulation M2 has come up with so far.
Some of the SNES and Genesis emulators have the widescreen feature but the games were designed with original aspect ratio in mind so there may be issues with that emulation feature. To get a true widescreen experience for SNES/Genesis games on those emulators, the games will need to be modified with widescreen in mind with the modification saved as a patch for the roms. But in case of Darius 1 & II, why would you want to come up with a widescreen patch for Genesis version of them when you can experience the arcade version instead? Just buy the compilation game or something like Darius Cozmic Collection for instance.
Like the previous M2 Shot Trigger games, some of the game modes for G-Darius HD are exclusively new which included M2 modifying the games with their own feature additions and other stuffs. As G-Darius Exhibition is an experimental game mode on what it's like to have a dual-screen game just like the other Darius games in the arcades excluding Darius Gaiden, only the boss battle feature made the cut although not all bosses are present in that mode. It's an awesome addition but if only it includes the whole game.
There was even a campaign taking place at Tsukumo PC shop's second floor at Akibahara where the Steam version of the game was being demonstrated there in G-Darius Exhibition game mode, allowing people to experience the ultra-wide gaming with sub-woofer installed in the seats. Sub woofers installed in the player's seats of the arcade cabinet have been a thing ever since the original Darius hit the arcades. Darius Burst Another Chronicle is the latest to have the similar cabinet setup. Like Darius I, II and Darius Burst Another Chronicle (Part of Chronicle Saviors) PC versions, there will be support for multiple monitors for G-Darius Exhibition game mode for G-Darius HD.