i've thought about this topic for a very long time. the reason being is that it... for some reason was hard for me to put into words which i'd prefer over the other. allow me to explain:
i think this might be the hardest comparison for me to do out of every remake so far.
i have a confession to make here: i've never played the originals. while they are available digitally, i've never really had the time nor inclination to play them all that much, so i've never got to experience what they were like. due to this, i can't say for certain whether FRLG would've provided a better experience for me. sure, it's better in a "it doesn't have nearly as many bugs"- sense, but as far as enjoyment goes, i can't properly compare these two.
i will say that i did not enjoy FRLG for what it's worth. the best part of the game for me wasn't even the main game, it was the sevii islands and the stuff to do there. it just wasn't a very fun remake for me.
this one i can say a bit more on, since i've started with gen 2 (although to be honest... it's been quite a long time since i've played through original johto). i've loved HGSS and what it had to offer, and i don't even know where to even begin! pokeathlon should be a permanent addition to pretty much every pokemon game, as i love mini-game type things so i'm not stuck battling all the time. also, HGSS had the battle frontier AND pokemon following the player so yeah, it wins pretty easily in my eyes.
GSC was fine, and i think i prefer its old school pixel style to HGSS in some areas, but i can't ignore what HGSS brought to the table for me. nostalgia doesn't win, here.
oof. this is a tough one.
there are some parts of ORAS i was disappointed to see that really would've otherwise made it an outstanding remake, to me. i think staying too faithful to Ruby and Sapphire to a fault somewhat hurt it. don't get me wrong, i think the delta episode was really cool, but it bummed me out that there was no re-matching or interacting with Zinnia period, after that. it's just a one-time and done thing. aside from the delta episode, everything else seemed like vanilla ruby and sapphire with upgraded graphics and newer pokemon. to ORAS' credit, i think the punching bag thing from XY was carried over, so that was neat (but i guess that was more of a gen 6 in general thing than ORAS specifically). primal forms are a neat introduction, and it introduced very cool mega evolutions. and i would be very remiss if i somehow didn't mention soaring.
goodness soaring. one of the best experiences i've ever had. why is it so hard to skip the boring fly animations and soar? why couldn't game freak do this for subsequent pokemon games? it's not like hoenn was a super tiny region that somehow made it easier to render in overworld compared to others, right? i dunno. for me, soaring was the highlight of ORAS and i miss it to this day.
for me, this comes down to a tie between Emerald itself and ORAS. original RS was meh and unmemorable to me. i honestly gotta give credit where it's due to ORAS despite its shortcomings (really didn't like that battle frontier tease, game freak...), but it only beats out original RS for me.