While I don't need to buy this myself, I'm *very* happy to see the best version of Gen 2 (and my favorite main series game, period) now available on modern hardware.
IMO, Crystal still has plenty of things going for it over HGSS, such as the female protagonist (and most of the character designs, really) and portrayal of the Suicune lore. I also love its animated sprites, and think they look sharper and livelier than most of the ones from the GBA/DS games, despite having fewer colors.
I would second this - while I'm more likely to play HGSS and I think they're some of the best in the series, I personally think that the omission of Kris is one of the worst things to have happened in a remake so far. I grew up with the second generation - all the fun battles, glitches, stories, and experiences that I started out with were in Johto. So, in line with that, I was extremely pleased to see that HGSS were such faithful remakes of the original games, but so deeply let down with the very strange overwrite of the first female player character, especially since I liked her so much.
As for the graphical integrity of the game, I think that a major factor was the coloration. Crystal corrects a lot of sprites' color errors and has more saturated colors overall, and appears brighter and sharper as a result. The original Johto games were a step up from Gen I, but didn't use their technology to full capacity in many ways.
The one thing that I think this VC release could improve upon is localizing some of the features that never made it into the English version of Crystal. They could bring back the Pokémon Communication Center, even if it's non-functional; allow the GS Ball event to occur in-game; and perhaps tweak small localization errors like the Odd Egg's shiny rate. So far VC releases have been almost 100% direct ports, leaving even major glitches in-tact, but this one could be made better with just a couple tiny changes.
Not going to happen. The 3DS has major emulation issues with GBA games, and can only simulate them natively, which cuts out a ton of features (including even sleep mode). This is a big reason why we got ORAS in the first place -- lack of GBA VC meant that remakes were literally the only way to get Hoenn on the 3DS.
Now, the Switch VC is a different story, and I think it's very likely that we'll get RSE and FRLG (along with RBY and GSC returning from the 3DS) re-releases there. The Switch can't play DS/3DS games, nor even emulate them (due to the lack of a second screen), so VC re-releases of GSC and RSE may be the only realistic way to have Gens 2 and 3 available on that console.
I do want to note that the article does say "Alas, it's
unclear whether or not Nintendo can overcome the problems that currently keep Game Boy Advance games off the 3DS's Virtual Console." So I wouldn't count it out completely yet, though I'll concede that the likelihood is extremely slim.
In that case I do hope that we get more VC releases on the Switch. I'm not sure if it has the right hardware to do so, but there
may be ways to just use one screen of the Switch to display both screens of DS games or something, since it's a touch screen - though I don't think my dream of every generation on one console could happen, since I doubt it can efficiently emulate the sixth and seventh generations. Oh well!