how is this game on 3Ds? does it fill the entire screen?
No. It retains the original 4:3 aspect ratio. There aren't any versions anywhere of the original games that have widescreen format. There is an option to add arcade style side bar art so the areas on the sides aren't just black space.
From a technical perspective, the games are somewhat disappointing. There are subtle framerate issues. Usually these are not noticeable (except MM5, which is solved by switching from NA/EU version to "Rockman" JPN version) but if you have a sharp eye you can see it, similar to Bloodborne. Ultimately the games are playable and enjoyable but the frame issue is disappointing. On the positive side, the coloration is good, clean and clear, unlike the VC versions of the games which include an inexplicable dark filter that muddies the colors.
The extra features are nice. There are save states, "encyclopedias" of characters and enemies, art galleries, and music players for each game. There's also a challenge mode which includes stage remixes (very minor, usually just different screens from different stages chained together in new ways), boss rushes, and so on.
While I was disappointed by the frame issue, the overall package and price is good and I'm not unhappy with the purchase.
